Interplanetary Wars

A project page on everything related to the Interplanetary Wars and related conflicts in the 2100s. Mostly still used as an info dump for info yet to be added to proper pages. As this is a project page, all information here is still in flux.

Related pages:
 * Human history
 * ZGene

Name
Some historians use the contemporary "Interplanetary War" to refer specifically to the conflict fought between 2164 and 2170, though most interpretations use the plural Interplanetary Wars to describe the entirety of the conflicts taking place roughly between 2150 and 2170.

Development notes

 * The story relevance of the IPW is that it represents a period that is both a transitional and formative one - the only time in Halo's history when all of humanity isn't dominated by under a single government and you actually have reasonably established polities that can challenge the UNSC. It can be used to explore how the UEG and UNSC started on the path we later find them on.


 * The tone of the IPW era is much "harder" in terms of the sci-fi aspect - Halo has never been hard sci-fi, but since the IPW is an early period, we can explore what kinds of tech the UNSC had before they had things like artificial gravity and drives that can take you from planet to planet within hours. The tech of the era is an in-between from here and now, and in some ways closer to today's than 2552's tech. It may not be Atomic Rockets-compliant, but it's at least aware of what Atomic Rockets has to say.


 * Aesthetically, IPW-era tech is meant to look much more "archaic" than that in the 26th century, with inspiration taken from both modern day and Space Race/Cold War era space technology, along with 70's and 80's science fiction illustrations. It's supposed to be bulky, cramped, unrefined, and lived-in. Some semi-quaint terms like "atomic drive" are used to further get across this impression.

Background
The Interplanetary War was the culmination of a few decades of economic downturn and unrest that followed a century of unchecked progress and expansion into the Solar System, known as the Golden Age of Space Colonization, or derisively as the "Space Bubble". While many factors ultimately led to the end of this era, the largest obvious catalyst was the ZGene crisis of the 2130s, which saw the gene therapies that had allowed humanity's rapid expansion into space turning against them, hurting many of the space-borne colonies in particular.

Humanity's first space colonies (and thus space-borne polities) were born under very different circumstances than those later established during the UEG's reign. Toward the midpoint of the 21st century, space technology began to advance rapidly, too fast for legislators to catch up. The ambiguities involved with different parties—nations, corporations, and even individuals laying claims to celestial bodies or their resources under outdated and vague legislation such as the Outer Space Treaty led to many disputes over ownership. For nearly a century, the majority of these disputes were resolved via peaceful means. Rather than holding colonies in an iron grip, many nations sponsored independent colonies with the presumption that those colonies stayed friendly to them rather than to their rivals; this sort of "soft power" was widely regarded as cheaper and more politically expedient than staking a claim to territories the Earthbound nations could only partially control. However, the obvious weakness of this approach was those colonies' vulnerability to fast-growing extremist movements, which may have altogether different ideas than the governments Earth had sponsored. The colonies also became a common outlet for Earth nations' political conflicts; one country might influence independence movements on a colony founded by a rival nation. This led to many colonies becoming either autonomous or sovereign in all but name. Such political conflicts became most prominent in the first half of the 22nd century, as the initial excitement of the Golden Age of Space Colonization began to die down. The rise of extremist factions in the mid- to late 50s saw Earth nations attempting to reassert their control on the colonies through military action, which was poorly received and led to increased sympathies for dissident movements among the colonists. Although it was not the first nor last conflict in the Sol system, the Interplanetary War was by far the most notable one, directly informing the political attitudes that shaped the UEG. The war and the events leading up to it were frequently used to justify the UEG's hard line against colonial separatists. Even centuries afterward, the development of the Frieden and Koslovic movements served as a cautionary example of what would happen if colonies were allowed to secede and develop independent of Earth control.

At the time, there was no single central authority in charge of the colonies, or even a common, generally agreed-upon forum for setting common rules; there were various attempts at such, but they were more akin to clubs of a few nations or colonies. The UN tried to act as a mediator, but its authority was not universally recognized, especially on the colonies; in addition, many of its regulations and rules were virtually unenforceable in many areas of the system. Many colonists saw the UN as an outdated Earth institution that looked out for Earth's, rather than their own, interests; it didn't help that the vast majority of colonies were not represented in the UN, as they were still provinces of their parent nations, even if in name only.

Throughout the late 21st and early 22nd centuries, conditions on Earth began to deteriorate, with overpopulation, food shortages and a global environmental crisis. The rise of sea levels rendered many coastal cities uninhabitable, causing mass migration, or necessitated expensive seawall projects. This led many Earthers to migrate into already-existing offworld colonies, creating a divide between their original pioneer colonists and the newer Earth-born migrants. Interplanetary megacorporations, many of them outside the reach of Earth-bound authorities, would often hire migrants in search of a better future for cheap labor. Though there were exceptions, in many places the working conditions and worker rights were abysmal, particularly for the colonists who had arrived in the later waves.

For much of the Golden Age, wages for asteroid miners (or any space-borne workers) were almost astronomically high. Everyone working in space was a highly qualified expert with an expensive education, and they were only replaceable through great cost. Ironically, the pioneer spirit—the colonists' famously large families—contributed to those colonies' own economic downfall. The corporations the colonists worked for were eager to sponsor offworld educational institutions to train more colonists to work in space, but after three to four generations, there was more supply of fresh workers than demand—particularly due to the escalating off-world mass migration from Earth in the late 21st and early 22nd centuries. In the first and second generations, it was more conducive for colonies to make more people in situ than to carry more people there from Earth. Over time, such concerns began to loosen up as orbital transit costs went down, which led to Earth migrants' numbers rivaling or even outnumbering those of the colony-born. As political unrest, war and subsequent economic recession hit Earth in the turn of the 22nd century, many nations and corporations became more cautious in their peacetime space endeavors. And as the third and fourth generations of offworld colonists matured, they for the first time found themselves either working with substandard wages, or unemployed—a concept previously unheard-of among colonists. Some academics, including Vladimir Koslov, saw these issues coming before they truly hit. The Koslovics campaigned for interplanetary workers to band together against megacorporations to secure their interests over two decades before the wages and working conditions truly began to nose-dive, seeing these as the last moments for action. However, as the spacegoing laborers remained generally well-off, they were widely dismissed as doomsayers and alarmists; the Koslovic movement did not truly take off outside the emerging Martian intelligentsia until conditions deteriorated in the wake of the ZGene crisis.

Most colonies aimed to be self-sufficient, but for various reasons were so only to a degree; in addition, with the unique resources of different outposts, it paid to specialize and trade with other colonies for goods, or sell them back to Earth. For a time, such interdependence was the order of the day, and most colonies prospered. As time went on, a lot of the interplanetary economy started happening between habitats and colonies rather than going back to Earth. This led to various Earth corporations re-establishing themselves in space the first half of the 22nd century, leading to them interfering with the often delicate balance that had formed in the inter-habitat economy. As colonies' formerly prosperous relations grew sour, the interplanetary economy began to suffer. Habitats weren't as readily willing to trade resources, or demanded higher prices and tariffs. This led to attempts by colonies to increase their self-sufficiency. For example, one of the reasons for the rise of the Frieden movement was their promise of creating a self-sufficient economic union of the Jovian colonies to ensure they would stay afloat in the crisis, especially if more colonies fell under Koslovic control.

Affecting in the background of the wars was also a civilization-wide crisis of identity, or rather numerous micro-crises thereof. Expansion during the Golden Age had been extremely rapid, too rapid for most societies to catch up. Even independent of space travel, the strength of the old national identities was generally in a steady decline; much literature and philosophy, especially in the colonies, was about this—why would the colonies be loyal to Earth when not even most Earthers were really connected to their heritage? On colonies settled by multinational efforts, the colonists' ties to their parent nations were extremely tenuous from the start. The reality of early space travel also meant colonial communities were extremely tight-knit, and the shared experiences as pioneers connected the colonists more than their Earth heritage, something that faded yet further into the background with the rise of the first and second space-born generations. Colonist worldviews and values were shaped by the realities of extraterrestrial life: the harsh pioneer conditions gave rise to tough, utilitarian mindsets, regimented societies, and large families. Over this period, many of the values and societal arrangements once taken for granted on Earth were reassessed and reimagined. Even as colonist societies progress past the pioneer stage and standards of living improve in the larger colonies, the pioneer mindset and the values established in the early period stuck. Despite the efforts of the UN and a handful of member nations to foster a common human identity, reception to this was mixed even on Earth, and it took the rise of off-world threats who threatened most of Earth's core values to finally united much of the planet under a common cause sometimes described as idealized pan-humanism, which would come to define the UEG's culture for centuries.

It did not help that communication delays and limited data-sharing protocols (the Solar interplanetary net was just emerging) meant that bubbles formed more easily in the small, tight-knit societies of the colonies. This was especially true in the outer system and the colonies around Jupiter and Saturn. Misinformation was even more difficult to correct than it used to be, as political demagogues might spread malicious propaganda for hours before the rest of the system was even aware of it.

21st century
Note: The timeline is assumed to diverge from ours around the early-to-mid 1990s, and the projected advances in space travel and colonization and purposefully very optimistic to allow for the kind of human space presence a large interplanetary conflict in the 2160s would require.

~2020s-2030s: The first steps of the Solar System gold rush: Pioneering efforts in colonizing Earth's orbit, mining near-Earth asteroids, and settling Luna and Mars inspire an increased interest in space exploration, and the race for the near-infinite resources of the Solar System spurs various technological advances by corporate and national actors alike.

~2040s-2050s: The Golden Age of Space Colonization begins: The permanent human presence in space begins to increase rapidly with a dramatic reduction in orbital launch costs. The Lunar and Martian colonies become fully self-sustaining while new space habitats are being constructed by the dozens. The challenges of spaceborne living, coupled with the untapped resources of the system, spur numerous advances in various fields, including medical science and AI research. The challenges of low-gravity habitation and even radiation exposure are overcome by revolutionary gene therapies which enable millions to live in space by the end of the century.

2060s-2070s: The first permanent settlements in the Asteroid Belt and on Callisto, with the latter being used as a base of operations to launch missions around the Jovian system and Jupiter's trojans. Soon after, the first colonies are established on Europa, Ganymede and Io by various corporations wishing to exploit the resources of the Jovian system (including the gaseous atmosphere of Jupiter itself), as well as to establish footholds for expansion beyond Jupiter. Since journeys to the outer system take months, the distant Jovian colonies mostly exist in isolation from Earth and Mars.

2090s:
 * The first permanent colonies are established on Titan and select other Saturnian moons, mainly by Jovian-based corporations.
 * Tensions heighten in a cold war between China (and various allied nations - potentially Russia + some East Asian countries) and the Western bloc/NATO. Unrest and uncertainty increase on Earth.
 * Around this time, the underground facility Crow's Nest is constructed in Kenya, East Africa and used as a base of operations by NATO.
 * The United States of America is dissolved and is later reformed into the United Republic of North America, along with Mexico and Canada.

As conditions on Earth slowly deteriorate, with political unrest and an ecological crisis, the colonies continue to flourish. Millions migrate to the offworld colonies in search of a better future.

Around this time, the escalation of Earth's ecological crisis as well as subsequent global unrest and population displacements, coupled with the challenges of policing the expanding frontier of outer space, prompt the United Nations to become increasingly involved in overseeing Earth's national governments and corporate entities, especially off-world. However, its increased oversight, coupled with accusations of partiality, draw significant criticism against the organization and breed polarization on Earth.

22nd century
c. early 2100s: A major war on Earth between China and NATO. At least parts of the war take place in East Africa, though there are actions across the globe and in orbit.


 * Early 2100s: NATO first establishes the early iterations of Orbital Drop Shock Troopers, then known as Drop Jet Jumpers. (There are many differences in doctrine and deployment methodology dictated by the technology of the time, but the traditions later port over to the UNSC)


 * A few earlier turf wars and incidents between nations on the colonies

2132: The ZGene Fiasco goes public. Public opinion on many of the off-world colonies turns against genetic modification, and various governments implement legislation to regulate rampant modification soon after. The resulting economic downturn on many habitats feeds extremist political ideologies and various conspiracy theories turn the public increasingly against Earth and the United Nations. As economic recession and unrest wracked the colonies, minor proxy wars and political demagoguery began to escalate tensions on both the colonies and Earth over the next two decades. With Earth itself struggling with internal divisions, many of its national governments lost their hold on their space colonies, many of which declared themselves independent over this period.

With Earth largely dealing with internal issues at the same time, crime, corruption and political extremism begin to fester on the colonies. Some colonies use the chaos to declare themselves independent. The recession polarizes relations between large corporations and blue-collar workers, and strikes and protests often escalate to violence. With local law enforcement often minimal, inefficient or increasingly corrupt in places, civic militias emerge on many colonies to meet riots, crime and violence with vigilante justice. While varied in their political composition, most of these "protector guards" position themselves against the Koslovics. Such militias become particularly notable and politically powerful in the Jovian colonies, eventually coalescing into the Frieden movement. Not all of them radicalized, however, and some (particularly those in the Asteroid Belt and on Luna) never saw eye-to-eye with the Frieden. Despite their often independent mindsets, some colonist militias would later ally with the UNSC during the Interplanetary War against either major extremist faction. Regardless of such exceptions, however, neutral actors find it increasingly difficult to operate in the politically charged environment, and many were pressured to pick sides. Even as extremist political groups took power in many places on Luna, Mars, around Jupiter and in the Asteroid Belt, Earth nations were hesitant to involve themselves directly, or would use the colonies and the emerging political movements there to fight their own proxy wars. Once those nations realized they had overplayed their hand, it was already far too late.

Corporate security forces open fire on rioting Martian workers at Hellas Planitia, resulting in dozens dead. While the UN investigates the incident and condemns the actions of the security officers responsible, the response is widely seen as a joke by the Martian underclasses. The incident is widely cited as a catalyst for the increased radicalization of workers on Mars and across the system, paving way for the Koslovics' rise to a prominent force; still, at this point interplanetary workers' activism is not yet as centralized under the Koslovics in particular.
 * 2142

Widespread strikes and riots take place on Mars, with miners demanding better wages, working conditions, and political reform. Dozens of political movements compete for attention, and local movements are often spontaneous and not yet centrally led. Many activists are killed or imprisoned, which leads to further resentment and legitimizes the activists' concerns. Around this time, Vladimir Koslov is killed while addressing a crowd, turning him into a martyr and fueling a cult of personality around him. After a brief power struggle, the Koslovic movement's leadership soon stabilizes under his co-revolutionaries. Turning Koslov's death into an effective propaganda tool, the Koslovic movement continues their spread, eliminating, subverting or absorbing various lesser or competing political groups; many moderate Martian cooperatives are subverted by Koslovic demagogues, or intimidated into aligning themselves with the movement.
 * 2143-2143

Precipitated by confusion caused by a proxy conflict between regional polities and a mining conglomerate, a Koslovic rebellion in Mars' Argyre Planitia starts a domino effect of successive revolutions and political upheavals which leaves several of the Martian settlements under effective Koslovic control. This inspires copycats elsewhere in the system and cements the Koslovics' status as the most successful revolutionary group in the system, with Mars becoming the nexus of their operations.
 * 2149-2152


 * 2150
 * Self-declared Koslovic revolutionaries increase their activity in the Jovian system, operating particularly out of newer, les well-off colonies on the minor moons of Jupiter. Determined to stop the spread of the Koslovic ideology on the Jovian colonies, various militia groups form a united front under the leadership of Nadja Mielke. This marks the birth of the Frieden movement as an organized force, and the rise of militant pan-Jovianism as a prominent ideology among the politically and ethnically disparate colonies on the moons.

A corporate-backed coup led by Nadja Mielke sees the Frieden movement rising to power on Ganymede.
 * 2153

The Europan colony of Thynia opens diplomatic relations with the Martian revolutionary republic, making it one of the more prominent colonies (that are not overtly under a Koslovic regime) to do so. In response, the Frieden level the Martian embassy a few weeks later, accompanied by various acts of political violence against Koslovic sympathizers (real or imagined). UN colonial advisors are dispatched on Io and Callisto to combat the movement's spread across the Jovian system.
 * 2158

A Frieden terror attack on Phobos followed by failed strikes on Koslovic targets on Mars further inflames tensions between the two movements. The attack also serves as a startling wake-up call of the Frieden's reach and military capability. As they avoid coming to blows with the UN, however, many on Earth still continue to downplay the Frieden's significance, with some even viewing them as a necessary evil. Meanwhile, the attacks polarize attitudes on various colonies, leading to further violence between Koslovic and Frieden supporters.
 * 2159


 * 2160-2161
 * The Jovian Moons Campaign. In their efforts to gain full control of the Jovian system under the pretext of eradicating Koslovic cells hiding in Ionian industrial centers, Frieden militants expand their influence on Io, finally coming to blows with the UN's colonial advisors and their colonial militia. The situation quickly escalates and leads to an all-out massacre of the UN forces on the moon, a ruthless purge of their affiliates, and a Frieden military takeover of the colony. Though not the first instance of Frieden on UN violence, it is the most notable and shocking one, making it impossible for Earth to ignore the movement's spread. A multinational UN task force follows several months after to reinforce the decimated Earth forces, with limited success. In the chaos, Koslovic revolutionaries attempt to establish themselves around Jupiter, leading to further bloodshed. This marks one of the bloodiest conflicts on the colonies so far and results in a relative stalemate, leaving the Frieden movement in uncontested control of some of the colonies on Io, as well as retaining their footholds on Europa, Callisto and Ganymede.


 * The outbreak of violence on the Jovian Moons escalates tensions in the system, and sparks various offworld proxy wars between colonies sponsored by Earth nations. This in turn leads to political and eventually military conflict on Earth.


 * 2162
 * February: The Rainforest Wars begin as various political movements and national governments clash over ideological differences in South America, while the UN attempts to manage the crisis with limited success. This sparks further conflicts off-world and leads to a considerable civilian death toll and ecological devastation. While the focal point of the fighting is in South America, there are conflicts across the globe. These conflicts are very muddy (politically and literally), and exacerbate Earth's existing problems.

Emboldened by the chaos on Earth, Frieden forces consolidate themselves on Luna, establishing a major foothold to strike against Earth and UN-aligned Lunar states as retribution for the Jovian Moons Campaign. Frieden forces on Luna eventually appropriate civilian mass drivers and target Earth with kinetic bombardment. Though no major cities suffer direct hits, impacts in the oceans lead to tsunamis and flooding with the breakdown of seawalls, leading to an alarming death toll. The United Nations declares a global state of emergency.
 * 2163


 * Jovian corporate wars. As the Frieden movement faces closer Earther scrutiny as a result of the recent events, many Earth corporations covertly backing the movement are effectively forced by the UN to withdraw their support to what is now recognized as a full-fledged rogue state. Many clashes occur around Jupiter and its moons between Frieden forces and various corporate security forces serving either Jovian or Earther interests. Eventually, the Frieden forcibly seize the assets of the few companies which cut off their support.


 * May:
 * The United Nations issues an emergency resolution establishing the United Nations Space Command. All space-borne national military forces are subordinated to the UNSC for the duration of the ongoing crisis. A small number of nations or rogue elements thereof resist the handover of power; though most incidents do not escalate beyond tense standoffs, fighting does break out in places.
 * The Lunar Campaign: UNSC forces are first deployed on Luna to eliminate local Frieden and Koslovic forces. While progress is initially slow, the tide eventually turns in the UNSC's favor.


 * November: Nadja Mielke, the leader of the Frieden movement and Hegemon of the Jovian Autarky, is assassinated in what is ostensibly a Koslovic attack on her way to a command center in the Europan city of Pelagon. This enrages the rest of the Frieden movement, prompting them to commit various retaliatory strikes against the Koslovics on Mars. Following Mielke's demise, her nephew, Oscar Bauer, emerges as the movement's most prominent leader.


 * December:
 * The Mars Campaign: A large task force deployed by the UNSC arrives at Mars, launching blitzkrieg-style attacks on Koslovics at the Argyre Planitia industrial sprawl. This marks the first major off-world deployment of space-borne marines, informs future military doctrine considerably, and proves the effectiveness of the UNSC as a jointly-led organization.
 * The Battle of Delambre on Luna sees the Frieden movement effectively eliminated on the Moon. With the UNSC closing in on their position, fighting breaks out between hardliners and reformist elements within the Frieden movement, with the few survivors forced to surrender to the UN forces. This also marks one of the first signs of the Frieden movement's splintering.


 * 2164
 * The Rainforest Wars have largely subsided, though minor actions against guerrilla rebels and rogue states continue on Earth.
 * The success of the Mars Campaign spurs a UNSC propaganda campaign and military buildup on Earth, with increasing resources now funneled to the UNSC. This is effectively the birth of the Earth-based patriotism that would shape much of the UNSC's and UEG's cultural character. The UNSC begins a systematic drive to crush the remaining Koslovic and Frieden strongholds across the system. Space warfare technology and tactics advance at an unprecedented pace.


 * 2166
 * November: The Mars Campaign concludes after two full years, ending with the eradication of all Martian Koslovic opposition. The conflict continues in various habitats of the Asteroid Belt as well as further out-system.


 * 2167
 * January: Following prolonged fighting between Koslovic and Frieden forces on Ceres, UN forces arrive to pacify the colony habitats on the asteroid. Most of the rebel elements are eliminated within a week, though holdouts retreat deeper into unmapped warrens of the asteroid, continuing guerrilla strikes continue for months.

Further battles around the Jovian colonies on Ganymede, Callisto, Io and Europa between the UNSC and the Frieden eventually lead to the latter's defeat in their most noted stronghold with the prolonged Siege of Europa, though Frieden resistance continues deep in the subsurface warrens that comprise most of the colonies. With the Frieden forces having a significant home field advantage, these battles are brutal and costly, leading to significant casualties both military and civilian.
 * 2167-2168

Battles at Titan and various minor moons of Saturn see the defeat of the Frieden movement as an organized force.
 * 2168

By this point, the Frieden movement is effectively dead; most supporters have either gone to hiding or turned coat, and all that remains is to mop up the few cells or splinter groups who continue to fight.
 * 2169

The last holdouts of the organized Koslovic movement are eliminated within the Asteroid Belt and near Jupiter, and the surviving members are apprehended. With the Callisto Treaty, the UNSC is given complete military jurisdiction over the off-world colonies. The war has left significant swathes of Earth and the colonies devastated, and there are widespread famines and population displacements. To tackle these problems, as well as to address various issues inherent to the organization, the UN is reorganized into the United Earth Government, with the UNSC folded in as its military arm.
 * 2170

The war is followed by a reconstruction period lasting in many ways until the end of the century and beyond. After the war, the recognition of worker rights and the means to oversee them, clear and standardized negotiation policies, the increased regulation of megacorporations' activities, de-radicalization of unions and citizen militias gradually solved many of the underlying issues that had given rise to the Koslovic-Frieden conflict, though tensions lingered for generations.

Unassigned/planned events

 * Liberation of Rio de Janeiro (part of the Rainforest Wars, pivotal battle)

Earth and the United Nations
By the first half of the 22nd century, the UN had assumed an active role in managing various crises on Earth, including overpopulation, an ongoing climate crisis and consequent conflicts, as well as overseeing off-world colonial development across the Sol system. This development had prompted the organization to become increasingly involved in individual nations' affairs. Since some nations were more eager to push this "United Earth project", seen by many as a development toward a global federation, it created rifts within the organization which in turn spurred reforms that made the UN more decisive, and its resolutions more binding on the member states. The Security Council will have undergone a reform, removing the veto power of individual members and making decisions via majority vote, which will have been controversial but also allows them to actually do things. By this point, the UN may also have established a parliament as a more effective deliberative assembly.

Meanwhile, many off-world groups saw the organization as ineffectual or corrupt; corporations seeking autonomy from Earth authority resented the regulations and oversight it imposed on bio- and nanotechnologies, while a disgruntled laborer class that had built up on the rapidly growing industrial hub of Mars and various Asteroid Belt outposts considered the UN to be a symbol of Earther oppression and bureaucratic bloat that turned a blind eye to their oft-squalid conditions, or the excesses of the megacorporations responsible for those conditions; the UN either was not doing enough, or was doing too much.

The UN's space presence was distributed among many organizations, with lots of bureaucracy and overlaps in jurisdiction. Before the UNSC and the buildup of 2164, the UN had no true military of its own, merely an interplanetary outgrowth of the Peacekeeping forces, which was wholly ill-equipped to handle the crises that would arise on the colonies. (e.g. pre-IPW, most of the ships the UN had were transports and glorified patrol craft.)

UN Colonial Advisors: officials of the United Nations tasked with colonial outreach, helping struggling colonies sustain, govern and defend themselves, as well as preemptively combating the rise of extremist movements by training and organizing locals in UN-sanctioned militias (similar to the UNSC's later Colonial Militia Training program). While initially established to cover most areas of colonial development, the colonial advisors' efforts became increasingly military-oriented with the rise of extremist movements such as the Koslovics and Frieden. The advisors' efforts only enjoyed limited success, particularly as many colonial populations became estranged from the UN, their sympathies turning to rebel movements instead.

The UEG's formation was both the culmination of a decades-old "United Earth project", and a long-overdue reform of the UN, with the UEG formed both as a continuation of the UN's ideals and out of seeming necessity in the face of the fallout of the war.

Notable leaders and figures
 * Emanuel Serra (Secretary-General of the United Nations at the time of the IPW)
 * Fabiana Stewart (Commanding officer of the Drop Jet Jumpers)
 * Ezekiel Lorentz (URNA, later UNSC Marine Corps officer)
 * Jeremiah Mendez (Member of the URNA Army, participated in the Rainforest Wars)

Earth geopolitics/factionalism

 * The UN is increasingly divisive around this period, and some countries will either break off or not participate in the UNSC/UEG project; this is also one of the causes of the Rainforest Wars.


 * There is a general trend toward larger regional federations on Earth in order to more effectively guard their interests in space colonization and the securing of off-world resources.


 * URNA, UK and EU (collectively as NATO) closely involved with UN peacekeeping operations in the buildup and eventually the formation of the UNSC, which leads to the UNSC drawing largely from Western (and specifically URNA/NATO) traditions, though various other (largely NATO-affiliated) countries are involved from early on (e.g. Australia, East African Federation, Korea, India, Japan?)


 * Other wars and geopolitics-shaking conflicts in the late 21st/early 22nd centuries? Note: all need not be dated exactly, especially if placed closer to the present day


 * Russia retains some power locally but is largely isolationist and has been in a steady decline throughout the 21st century, despite some spacefaring efforts; may have been embroiled in conflicts with some of the former Soviet republics and an economic downturn, which drove many Russians (e.g. Vladimir Koslov's family) to migrate into space colonies through foreign corporate efforts. In the buildup to the IPW, Russia (or its corporations/oligarchs) may be involved in some offworld or terrestrial proxy wars in a vain attempt to reestablish themselves.


 * Korean reunification at some unspecified point in history

The Equatorial Scramble
There is a growing shift in global economic hotspots toward the equator, as it is more advantageous to launch orbital missions there; this leads to both development of equatorial countries, but also the old powers attempting to exert their influence over those countries. Starting in the mid-21st century, global (and extraglobal) geopolitics have been shaped increasingly by nations' access to (or control over) equatorial launch sites, as this played a major part in their access to spaceborne resources. However, control of these launch sites was not often more directly exercised by corporations than the nations they originated from.

Overall, for much of the Golden Age, South America is the world's launch capital in terms of volume, with East Africa and the Indonesian archipelago trading places for the second and third.

Most notable bulk launch sites/spaceports on Earth:


 * The Americas
 * Alcantara, Brazil (?)
 * Guiana Space Center, French Guiana


 * EMEA
 * Malindi, Kenya


 * Asia
 * North Maluku, Indonesia

United Republic of North America
Federation comprising the former territories of Canada, Mexico and the United States. The union was born after at least one American civil war, though not known by that name (to do: name the war & establish roughly what it was about), as well as the unification of the "political remnants" of the US, Mexico and Canada. By the mid-22nd century, they have largely recovered from the fall of the US and the regional unrest that accompanied it—conflicts in or with Mexico and Canada as well, or at least one of them may have prompted them to band together to safeguard their collective interests. They have deepened their ties with Europe, with European countries exerting more influence within NATO, for example. Culturally, they are a mishmash of US, Mexican and Canadian influences (e.g. increased prominence of French and Spanish + various others e.g. Chinese due to its prominence in Canada and influence throughout the 21st century).

European Union
The EU's development towards a federation has continued, though some member states have seceded and/or rejoined over time. Germany and France hold most power; elsewhere smaller countries (e.g. Nordic Council, Baltic Assembly, Visegrad Group) have deepened their ties to better represent their interests. ESA remains their space agency, though a large portion of the Union's space power rests in corporations originally based there. The EU is economically and militarily powerful (particularly through NATO), but its nations' grip over their space colonies is more tenuous than they'd like to think, and in many places corporations are largely free to do as they wish without much accountability. Powerful lobbying and bribery at the highest levels of the EU government is partly to blame, and the crisis following the Frieden's backers coming to light does usher in a major crackdown of corruption within the union.


 * Status of the UK?

Commonwealth of Australia

 * One of the most ardent supporters of increased UN control, maintained a strong diplomatic and foreign aid presence.
 * Fell back on agriculture as its primary industry (which has made it a desirable trading partner due to food shortages) after the mining industry crash, but there is an industrial presence that was expanded over the 21st century.
 * Has a highly progressive society, but the public is at odds with the government's reluctance on migration and foreign policy.
 * Allies are Europe, NATO, New Zealand; has frosty relations with China and a number of nations in South-East Asia.
 * Public wants a pro-environmental stance; Australia has been criticised for being one of the last nations to move away from heavy use of fossil fuels (basically when the UN forced their hand). Only adopted nuclear fission for their starships.
 * Navy is 68-ships strong (1 battlecruiser with another laid up, 2 carriers, 1 landing ship, 13 destroyers with 9 laid up, 9 frigates with 18 laid up, 17 submarines, 21 patrol boats, 3 replenishment ships), with an additional 15 starships (1 base ship, 3 combat cruisers, 4 cloakers, 7 spaceplanes) in the Royal Australian Spatial Squadron. This massive military was spurred by the fall of the United States, and unlike previous designs, these were designed to be threatening. Premier Special Forces remains the Special Air Regiment of the Royal Australian Army.

China
China, which had seeded several space colonies in the initial wave, enters relative downturn after the war with NATO, at least in the global stage. Some balkanization may occur. Still, they remain fairly prominent, and likely try playing the two major factions in the colonies against each other while seeking to benefit from the crisis. They may end up overplaying their hand, though. The fact China doesn't contribute much to the traditions of the UNSC indicates it either wasn't very involved in the United Earth project, did not join until later, or wasn't in a position to dictate terms (the IPW may see a political reform or other changes).


 * China and Vietnam may or may not have some form of industrial/economic cooperation going on at this point or later, given the later prominence of SinoViet (though this could also come about later).
 * Tensions between China and the West remain fairly high by the mid-2100s, to the point of the two being engaged in a constant low-key cold war in the buildup to the IPW and fighting off-world proxy wars. Still, the rise of Brazil as a nascent superpower will shake up this balance somewhat.

South and Southeast Asia
South/Southeast Asian states (India, Philippines, Malaysia, Indonesia, Vietnam? etc) become fairly economically prominent by the first half of the 22nd century and are involved in space colonization (e.g. the Philippines have at least a couple of Martian colonies), though none are necessarily global superpowers or militarily very notable.

South America
South America, especially Brazil, increase in power as well, both globally and in space. Sparked by the ongoing divisions in space, tensions between UN-aligned and anti-UN nations on the continent eventually break out into violence in the Rainforest Wars.

Brazil (or potentially a coalition of South American states) may be attempting to become a superpower, particularly following the fall of the US. Its location makes it ideal for launching orbital missions, and cutting other nations off from its spaceports could serve as a powerful political statement. (There may also be something involving turning large swathes of the Amazon Rainforest into farmland.)

Politically, Brazil and several other South American countries may fall under communism (possibly the Koslovic variety, or closely related) in the first half of the 22nd century, which leads to them cutting ties with the West (esp. in regards to launch sites and whatnot), and backing the Koslovics off-world and giving them a solid foothold on Earth. This polarizes the South American political climate as counterrevolutionary right-wing movements pop up, some of which ally with (or are sponsored by) the Frieden. This in turn kicks off the Rainforest Wars.

Africa
Africa is the most populated continent by 2100, but while its nations are economically large, many are also dealing with internal issues. There is a NATO-China war in the 2080s-2090s fought partly in Africa over the continent's resources and strategic sites. This took the form of a cold war for several decades, and eventually escalated to a limited nuclear exchange, even seeing limited action in Earth's orbit. The cold war in the buildup led to the construction of Crow's Nest and components of an anti-orbital missile-defense system in East Africa - components of the same system likely exist elsewhere in the continent, as well as on other continents (Southeast Asia, South America?).

One of the more notable African states is the East African Federation (later folded in as the EAP within the UEG), a union of Kenya, Tanzania, Uganda, Burundi, Rwanda and South Sudan (give or take a few) formed in the first half of the 21st century; within the union, Kenya, Tanzania and Uganda are the most prominent. The EAF was closely involved with NATO's equatorial buildup in the late 21st century to the early 22nd, and remains a close ally; this arrangement also built up their own military forces, economy and infrastructure in the wake of the conflict, something that would later help their case in choosing the site for the first space elevator. By the mid-22nd century, they maintain their own (though NATO-compatible) spaceborne military and remain in something of a cold war with China.

Before and during the Rainforest Wars, Africa also sees a fair bit of political unrest and even armed conflict, as extremist-aligned elements (both within and without the political process) threaten to destabilize the some nations.

The Middle East
The gradual shift away from fossil fuels to a fusion economy over the course of the second half of the 22nd century likely sees the region diminish in its strategic importance, though some of its economies may successfully diversify themselves. Many will likely have undergone, or will have to undergo, major social and political reforms by this point, which may mean they'll be mostly busy dealing with internal issues.

UNSC
The early UNSC is an emergency force created in 2163 to deal with offworld unrest and threats to Earth; does not command Earth-based planetary forces until later. The UNSC is at first national spaceborne forces subordinated to a UN command (hence "Space Command"); membership was not optional for space forces, though planetside forces on Earth remained under the control of their respective nations. However, as the UNSC began to pick up momentum, starting in 2164 with the success of the Mars Campaign, more nations began to commit their forces to the joint effort.

UNSC branches only come about during the war in the buildup starting in 2164, when the UNSC begins to amass actual forces of its own. The UNICOM-NAVCOM divide may also come about at this time.

Notably, the UN's Earth-based elements were not under the UNSC's command until late into the war, and by then much of the fighting in the Rainforest Wars had already abated.

One thing that has been brought up is the creation of the Drop Jet Jumpers, the precursor to the Orbital Drop Shock Troopers. Since the ODST is considered a UNSC unit, there is an option for something like the DJJ to be operating in the IPW before they join the UNSC. They will probably come from the URNA and be called something like the URNA Drop Jet Jumpers Special Missions Detachment. They will deploy throughout the Rainforest where they make an exceptional name for themselves. I've debated on the topic of having them deploy to the Jovian Moons, but I am unsure of that yet. And they will deploy to the Mars Campaign as well.
 * Drop Jet Jumpers
 * Campaign Notes [SO FAR]
 * Jovian Moons Campaign - Advisory Role
 * Rainforest Wars - Advisory Role to Direct Military Action
 * Mars Campaign - Direct Military Action
 * Basic Notes about the DJJ include
 * A URNA Marine Corps Colonel (O-6) leads the detachment under the URNA Special Operations Command/UNSC Special Warfare Command.
 * They merge into the UNSC as one of the first major SOF units to join the organization.
 * Can be present at a number of conflicts that encourage a spotlight to be shone on them.
 * Conduct basically suicide missions that are URNA Marine Corps like SOC and SOF missions for the UNSC SPECWARCOM.
 * Main advantage is speed in comparison to conventional forces: by this point, there really isn't an easy and painless way to deploy troops straight into the action fast, especially against well-defended targets, and the DJJ are the first step toward that.

Koslovics
The Koslovics had activity throughout the system, but on Mars they became the most organized and prominent, even establishing a government and taking over several of the Earth corporations' operations there. Near Jupiter, Koslovic rebels were also prominent enough to make various Jovian-based corporations back the Frieden to get rid of them. While primarily an off-world movement, there were prominent Koslovic sympathizers among some Earth nations who opposed the UN's increasing control, and some Lunar city-states fell under Koslovic control for some time.

Prominent leaders and figures:
 * Vladimir Koslov - ideological architect and later most notable martyr of the movement
 * Eliza Kemal - the main political leader of the movement for some time after Koslov's death
 * Geraldo Aguiar - led the Martian Koslovics up until the Mars Campaign
 * Marlon Laksmini - Martian native and Koslov's former enforcer, suspected to be the real power in the movement after Koslov's death
 * Rene Lopez - commanded Koslovic forces on Luna and Earth during the Rainforest Wars, ambushed and apprehended by the URNA in South America in early 2163
 * Xiao Guiying - commanded Koslovic forces during the Mars Campaign, killed by UNSC bombardment early on

Frieden
Authoritarian and corporatist movement which campaigned for self-rule and self-sufficiency for the Jovian colonies and later other outposts on their own terms. Frieden at their height controlled the major colonies on Europa, Ganymede and the space around Jupiter, as well as resource outposts in the asteroid belt, around Saturn, and a major foothold on Luna.

Prominent leaders and figures:
 * Nadja Mielke - militia leader and later self-entitled Hegemon of the Jovian Autarky, assassinated in 2163 by Koslovics
 * Oscar Bauer - nephew of Nadja Mielke, became the movement's most prominent leader following her death; committed suicide to avoid capture in 2167
 * Bernard Horvat - led Frieden forces around Saturn in the final years of the war
 * Samed Budiono - leader of the Frieden cell on Luna, summarily executed by hardliner members of the movement in 2163 for proposing surrender to the UNSC
 * Celeste Renou - one of the military commanders of the Frieden on Callisto in the later phases of the war

Others

 * Minor polities on offworld colonies (planets, moons, asteroids and space habitats)
 * Non-UN-aligned Earth nations, misc. rogue states
 * Extremist political movements independent of the Frieden or Koslovics
 * The BioPurity League: a radical group calling for an end to genetic and biological modification; grew enormously in the wake of the ZGene crisis.
 * Mercenary/PMC groups

Technology
Human tech in this era is much more "grounded" and closer to the modern day than what we later see, with primary inspirations being modern-day space technology and concepts, along with a healthy sprinkling of Golden Age science fiction illustrations. More specifically, the Golden Age of Space Colonization (~2030s-2120s) is Rocketpunk-inspired in terms of optimism and even design in places, based partly on 50s/60s-era assumptions on how humans would spread to the Solar System. As the Golden Age draws to a close, things get closer to Halo's 80s-inspired design sensibilities.

Notably, even the few "exotic" technologies the 26th-century UNSC has are absent, like gravity manipulation, space stealth, or forcefields (not even the atmospheric shields depicted in Halo Mythos' IPW spread illustration). Interfaces are tactile and holograms are scarce and only seen in physically enclosed tanks filled with a reflecting gas medium.

This era saw one of the earlier uses of limited human augmentation, either temporary or permanent; e.g. Drop Jet Jumpers may have had to take specifically-tailored drugs to withstand the accelerations and decelerations necessary to their deployments, and both the Koslovics and Frieden likely used combat drugs and stimulants of some kind (some of which were banned after the war).

As a consequence of a development known as the "atomic renaissance", starting in the first half of the 21st century, nuclear fission reactors saw a lot of development over the 21st century. By the mid-22nd, nuclear reactors are safer and more versatile than ever (in terms of e.g. miniaturization). Though the emergence of fusion will soon see them relegated to a secondary role, fusion is still emerging and immature as of the IPWs, and fission reactors continue to be the go-to power source in space (and planetside installations) until the 23rd century. Overall, general attitudes about nuclear power are assumed to have grown more positive than today since nuclear is really the best option for a widespread space presence before proper fusion or more exotic energy sources like antimatter. Photovoltaics are widely used in civilian spaceships and infrastructure, and while they have developed considerably in their efficiency, but they are hardly viable for most military applications.

The wars saw a lot of technological development, with early-war vessels becoming obsolete within a period of a few years. Some war-era advances:
 * By the second half, fusion reactors may see adoption on large ships - the accompanying developments in fusion technology accelerate the shift to a full-fledged fusion economy also in the civilian sector
 * Propellant storage/compression advances; tank armoring methods. This may have divided schools of ship design: whether to have a smaller number of large, better-armored tanks, or compartmentalize propellant among a lot of small and light (but fragile) tanks.
 * Drive technology (e.g. the introduction of open-cycle gas-core NTRs)
 * Ship armor becomes more viable and more components can reasonably be armored with increased mass budgets
 * Countermeasures, esp. AI-driven/automated
 * Vacuum combat gear: rapid and reliable sealing methods, miniaturized RCT systems
 * Improved compartmentalization of crew/habitat modules
 * Improvements to the efficiency and durability of radiators

Orbital transit: early skyhooks/rotovators (even one around Earth?), mass drivers on low-gravity bodies (e.g. Luna, Jovian Moons)

Even otherwise unarmed dissidents actually have some natural weapons, e.g. point defenses against asteroids and micrometeors are fairly commonplace even on civilian vessels and colonies, on top of mass drivers, reactors and spacecraft engines; miners also have access to mining explosives. In fact, the call for the regulation of such technologies was a major political issue on Earth, and, in turn, the source of much protest for colonists.

Early cryo-storage may exist, having been developed in the second half of the 21st century for long-distance journeys (e.g. to Jupiter or Saturn). However, the unwieldiness and uncomfortable nature of the technology does restrict it largely to such long trips, or when a ship really needs to carry a lot of people and can't afford to keep them all awake.

AIs exist but remain a fairly new and emerging technology. Their categories have not yet standardized into "smart" and "dumb", and though what would later be known as first-generation "smart" AIs exist, their applications are very limited. Different nations and factions experiment with these but they have few to no effective tactical applications at this point (though this may change during the war?). "Dumb" AIs, though much less powerful than their later counterparts, exist and are increasingly common, though they are even more specialized and may not yet take the form of full-fledged personas with avatars and whatnot. Notably, AIs (particularly smart ones) are not portable, and permanently occupy large data centers.
 * Early smart AIs may be used as the central "brains" of a large station, colony or even a ship (e.g. a purpose-built automated vessel).

Ship design and aesthetics
The spacecraft used during the Interplanetary Wars were still a long way away from those of the 26th century. Not only had ship classes not yet solidified to the system we're familiar with, but they were also far more technologically crude. There were multiple different schools of ship design among different nations, though the craft built by the nascent UNSC during the Interplanetary Wars would already show hints of Halo's blocky design aesthetic. Spacecraft design was heavily dictated by functionality, even more so than in the 26th century; most ships were essentially constructed from a fixed set of modules whose functions were externally visible: fuel tanks, engines, radiators, sensor packages, weapon systems and ammo magazines, etc. Major distinctions include the lack of hyper-efficient fusion drives, which means large and cumbersome fuel/propellant storage; there are no hull-embedded heat radiator mechanisms, so radiators are likewise large and vulnerable; and there is no paragravity, so artificial gravity is either achieved by thrust and/or rotating carousel sections, meaning that ships' decks are arranged perpendicular to the main thrust axis, rather than parallel to it as on later vessels. As a general rule, warships are not designed to operate in atmosphere let alone land on a planet and as a result, are anything but aerodynamic. Some smaller spacecraft may be capable of landing on celestial bodies, at least low-gravity ones, but they would do so vertically, balanced on their main engine unit(s).

The lack of inertial dampening also means that warships must use conventional means to secure the crew during combat maneuvers; crash couches are standard, but some nations and factions may employ gel tanks in which the crew is fully submerged in order to allow more extreme maneuvers.
 * Even regular crews may want to use pressurized suits while in combat.

Underlying axioms of ship design
 * Due to the relative inefficiency of drive technology, mass budgets are still very tight, and so every gram counts. For most ships, the bulk of the ship's mass is propellant, the rest being divided among superstructure, reactor, engines, and weapons—the pressurized crew sections are a comparatively tiny part of a ship. This also means that crew-to-ship size ratios will differ from those in the later centuries (i.e. a ship the same size as a 26th-century equivalent will have a smaller crew, simply because there isn't as much livable space, and most of the size is taken up by propellant.)
 * Most ships have fairly narrow mission profiles and specializations (the earlier the narrower) - generalist ships are a luxury you can have with a bigger mass budget (there could be earlier generalist ships, e.g. atmosphere-rated spaceplanes, but they probably wouldn't be very good at any of their jobs)

Spacecraft types
Ship classes recognised by the UN (other nations have their own definitions). Note that these will all have a descriptor in front of them to denote their exact role (e.g. Hangar cruiser, battle orbitor, heavy lift spaceplane)
 * Orbitors - short-ranged orbit defense ships
 * Spaceplanes - Aerodynamic space-to-orbit patrol ships. Smallest of 'em all.
 * Cruisers - Long-ranged warships designed to operate for extended periods in interplanetary space. Typically larger and more powerful than Orbitors, though there are exceptions
 * Base ships - deployable stations and frontier command ships
 * Surveyors - Originally descended from civilian research craft, these are high-endurance reconnaissance ships with extensive drone capabilities for spy purposes.

Outside low-orbital missions, the traditional space fighter is largely absent at this point; smaller orbitor classes may act as corvette-analogues or something akin to the Longsword, but there isn't yet much of a niche in space combat for a low-endurance one-man fighter.

Landing craft
 * There may be two or more major schools of landing craft: that of the Space Shuttle-style "belly lander" and the classic vertical rocket (VTVL), or "tail sitter". For troop deployment, large, shuttle-style craft are usually preferred, though they are vulnerable to AA fire. There may be smaller versions, called assault boats, as well as specialized "drop jets" and other impromptu landing vehicles used by the ODSTs' predecessors - these range from single-use entry capsules like the Apollo command module to elaborate staged jet-assisted backpack systems based on the Skycrane concept.
 * Consideration: Nuclear-powered shuttles may be a good reason not to fire on them even if an enemy one is entering your atmosphere.

Nonstandard categories
 * Bugs - general nickname for numerous types of converted asteroid or comet mining craft or jury-rigged attack ships patterned after such vessels. Often inelegant but practical, constructed out of homegrown parts or standardized commercial modules and consisting of a skeletal girder frame, propellant tanks, engines, maneuvering thrusters, various manipulating appendages, and weapons, as well as a small hab module no armor to speak of.

Propulsion and travel times
Ships are painfully slow compared to the 26th century, with most interplanetary distances taking months to cross. At the start of the war, trips to Mars take around 4–5 weeks. To the Belt, around 3 months. To Jupiter, 4–5 months. To Saturn, 9–10 months. These figures have changed only incrementally since drive innovations in the mid- to late 21st century. All travel times are subject to the variance caused by the planets moving in their orbits. They may also be shorted by the use of additional chemical or atomic booster rockets in the acceleration phase. Travel times may be reduced to around 2/3rds by the late-war era.

No ship is yet a "torchship" - i.e. they can't just burn indiscriminately. More time is spent coasting than accelerating, and no engine is capable of constant high-g burns.

Despite various advances, surface-to-orbit transit is still far from trivial, particularly in the deep gravity well of Earth, and orbital missions remain costly. This has prompted the rise of space-based infrastructure.

Ships frequently use combinations of different engine types to maximize their respective benefits, while different factions may favor specific drive types either due to availability or tactical considerations. Some ships have separate sets of drives for long-distance travel (e.g. ion) and combat maneuvering (chemical/nuclear) to maximize the benefits of separate systems (high acceleration vs high specific impulse, though some drives, e.g. VASIMR, can alter between these). Many smaller craft lack an effective long-distance capability altogether, or must be fitted with additional propellant/reaction mass tanks etc.
 * Some ships have separate forward-facing drives dedicated to deceleration.
 * Staged chemical and ion - Uses chemical rockets for the initial acceleration, with ion engines for long-distance steering and deacceleration. Cheap and reliable, but difficult to maneuver when forced off-course due to combat maneuvers. Found on less and less ships as the IPW draws closer, probably was widely used on consumable colony ships.
 * Nuclear and ion - Uses a VASIMR drive for long-distance travel while eschewing chemical rockets for nuclear ones during high acceleration. Both drive systems likely powered by the same nuclear reactor. May be standard for cruisers and above as of the IPW.


 * Drive types


 * Ion drive/plasma jet: Futuristic VASIMR derivative. Slow to build up speed but good specific impulse; can also "shift gears" (i.e. trade specific impulse for thrust). Became the default option for long-distance spacecraft in the second half of the 21st century, and enables much of the interplanetary economy; may still be a commonly preferred option for long (interplanetary) trips, but has limited combat applications. Can only be used in a vacuum. Versatile and efficient, few mechanical parts. Near-exclusively powered by a fission reactor; fusion-powered versions are an emerging technology by the time of the IPWs, but remain expensive and are probably too unwieldy to be worth it; putting fusion reactors on ships tends to yield diminishing returns since the reactor and the machinery needed to cool it is so massive.
 * Many civilian ships, especially in the inner system, use solar power instead of nuclear, though this is insufficient and non-viable for warships.
 * Variants of the technology use hydrogen and/or other (finely-ground asteroid dust?) reaction mass injection into the exhaust for added thrust.


 * Atomic drives/fission torches: A form of nuclear thermal rocket; exact designs vary. Faster to accelerate than ion drives, but less efficient over long distances.
 * Closed-cycle: The traditional and safest form of nuclear thermal rocket. Some nations may use them for surface-to-orbit transit (better than conventional chemical rockets), but may still not be universally adopted due to safety issues and limited utility compared to chemical rockets as the thrust advantages are mostly cancelled out by weight. Standard for maneuvering drives.
 * Open-cycle: a full-fledged fission torch. Only usable in outer space. In military usage, the strategic advantage of superior thrust may outweigh the risks of failure and environmental hazards. Favored by some nations and dissident forces particularly for superior maneuvering capabilities, but due to safety concerns use is frowned upon by some nations, and regulated under the UN. (deep-space colonists and corporations may have fewer concerns)


 * Chemical rockets: High thrust but pitifully low specific impulse. Staged disposable tanks are often used, and virtually required. The default option for operations within a gravity well (surface-to-orbit transit), short-range maneuvering, and common for providing an extra boost in the initial acceleration in interplanetary-range missions. However, the widespread use of fairly mature fission technology has seen them increasingly replaced by nuclear rockets.


 * Fusion drive prototypes exist but remain non-viable outside laboratory conditions. Though nuclear fusion power has just started to become viable, the reactors are heavy and cumbersome machines, which limits their use beyond fixed groundside facilities or large space stations. As well, the limitations on reaction confinement methods at this point are a large technological obstacle for developing true fusion torches (which only come about in the ~2330s).


 * Solar sails are used on some civilian ships for long-distance cargo, at least in the inner system, but have few to no military applications

Tactics, strategy and doctrine of space warfare
By and large, warships are glass cannons, with most of the focus of defenses being on avoiding getting hit rather than absorbing hits. Early warships had little to no armor, except for the crew module; the reasoning was that any munition exchanged in space combat was likely to mission-kill a ship anyway, and every extra gram counted with the weak engines of the time. The best you could do was to compartmentalize parts. Better armor coverage may start becoming more of a thing during and partly before the IPW, though, particularly for vulnerable components like propellant tanks. Even before the wars, this may've divided different shipbuilding schools: whether to make lighter and more maneuverable ships focusing on countermeasures, or to focus on armor.

Heat management plays a massive role in engagements, as does delta-V. Combat encounters are generally short, with each side able to perform only a handful of moves before either overtaxing their heat radiators, exhausting their delta-v, or being mission-killed one way or the other.

By and large, course changes during interplanetary trips are highly undesirable and deviating from an established course too much may be fatal (as too much maneuvering will drain fuel reserves); once you've committed to a course (on interplanetary distances), you're set on it.

The lack of FTL communications means there is always a light lag present in interplanetary communications, which is noticeable even from Earth to the Moon. Coupled with weeks or months-long travel times, this makes the colonies (particularly those in the Outer System) very isolated indeed. It also means the defenders will know when an attack is coming well in advance, and gives them time to prepare. This also caused considerable difficulty in effectively stamping out minor resistance movements: even as cells emerged in different parts of the system, they may have had weeks or months to establish themselves before an effective response could be mustered. Only the UNSC occupation of strategic sites and the establishment of permanent garrisons eventually pacified the system for the most part, though minor terrorist actions continued for some time.

Infantry were often forced to fight in vacuum or near-vacuum environments, or habitats with a constant risk of depressurization, which prompted the use of bulky vacuum-enabled combat suits; vacuum combat gear was one of the technologies to advance most rapidly during the wars, with suits and weapons used in the early years becoming antiquated by the end.

Between heat issues and RADAR counter-deterrence advancements made in the 21st century, achieving true stealth is impossible in space outside a number of highly-specific scenarios; later advances such as the 26th century prowlers are assumed to use exotic technologies not yet available at this time. The general rule is that everyone can see everyone else at all times, and defenders will know an invading force is approaching weeks or months away, along with the size and composition of that force. The sole exception are minor engagements with guerrilla fighters with no reliable access to telescopes, which did occur substantially during the war but do not represent major battles. Otherwise, all-encompassing, largely automated and effective monitoring of space traffic is practically a prerequisite for widespread space travel and commerce, and not particularly difficult to implement or seize for any reasonably organized force.
 * The next best options for stealth are more geared toward deception, e.g. making a ship appear to be something it's not (e.g. a warship masquerading as a civilian vessel, though even this is impossible if it uses a military-grade drive). Decoys masking as full-fledged ships would be more trouble than worth, since if you can pass a decoy off as a real ship, at point you'd be better off making them into full-fledged ships.
 * In close orbital engagements around large bodies (e.g. planets), said bodies will obviously mask any activities of ships on the opposing side of the planet, but this is highly situational.
 * Rebel forces could try to use Jupiter's massive IR emissions to mask the movements of their own vessels in low orbit, hiding the size and composition of their force from afar.
 * Automated vessels could have limited stealth (e.g. no need to keep a crew warm), e.g. reconnaissance satellites or drones, but these would have limited utility (e.g. maneuvering highly limited, and transmissions will light up on a radio telescope). Stealthy recon operations would have to be planned months if not years in advance.
 * Chilled subzero shields and directed beams to lessen the effectiveness infrared scanners may have been used to temporarily jam sensors, though the technologies would have been limited and not widespread.
 * Hiding underground, under ice or underwater could still provide more effective options for stealth, and both major rebel factions will use their native terrain (Martian caverns and Jovian ice-warrens) to give them a massive home field advantage, along with the advantages already inherent to pressurized and semi-fortified subsurface habitats.

Locations

 * Earth, Luna, Mars and the Jovian Moons have a lot of orbital infrastructure and space factories already, and a good chunk of the war will also take places on such facilities in addition to planets and moons.

Mercury

 * Minor colonies

Venus
Terraforming Venus is still a serious consideration at this point, and there are scientific missions ongoing to figure out the specific details. That said, most of the human presence (which is in the order of a few thousand people) is scientific in nature, with only some commercial outposts and even a single resort facility. The vast majority of the colonies take the form of high-altitude aerostat facilities and orbital stations.


 * Hampton Station - former semi-permanent research station whose goal was to research and refine Venus' gases for use in terraforming, and attempt to determine new techniques for radical terraforming efforts. Later bought up by an Asian country and moved to the planet's Lagrange point and turned into a Blacksite for military technologies.

Earth

 * Goddard Station - the "Ellis Island of space", the gateway to the offworld colonies for many colonists

Composed of various city-states and corporate holdings founded throughout the Golden Age. Most are still tied to their parent nations one way or the other. Though there have been various initiatives to form a council of Lunar states and deepen their mutual ties, the ZGene crisis has soured relations between many of them, making Lunar politics a confusing mess tied both to Earth and the wider movements across the system. The most common site of Earther proxy wars.
 * Luna

Mars
A collection of colonies settled by various actors. These have very different approaches to settlement and habitation, and there is no unified terraforming project at this point because the various colonies can't agree on what to do. By the start of the Interplanetary Wars, many settlements have fallen under Koslovic control or influence, either through the free electoral process or violent revolution.

The Belt
The site of various colonies, both surface outposts and spinning habitats embedded within the rock.
 * Ceres

Site of a colony and a covert Koslovic command center
 * Juno

Jovian System
Also notable (along with Saturn) as a hotbed for secretive high-tech labs run by various corporations seeking to circumvent Earth's laws, some of which would be appropriated by the Frieden following the outbreak of the wars. Some corporations operating in the Jovian system and beyond were already very estranged from Earth by the mid-2150s; these were either owned by billionaires who had long abandoned Earth, or early colonial corporate dynasties who had made their fortune during the Golden Age. As many Earth-based megacorps eventually withdrew their support for the Frieden between 2160 and 2163, this led to corporate wars between them and the Jovian-based businesses continuing to back the Frieden. Ultimately, the Earth corporations were faced with the choice to either maintain their support, or lose their Jovian and Saturnian assets to the Frieden and their Jovian corporate allies.

There were shipyards in the Jovian system, used mainly for civilian purposes (e.g. launching missions to Saturn), though by the 2130s they also began producing local defense vessels, and were fully militarized over the late 2150s and early 2160s.

Helium/hydrogen gas scooping is done by scoop/refinery-ships operated from some of the Jovian moons? (These may also end up being the earliest fusion-powered ships). Permanent tethers are not yet possible in terms of materials science. Maybe some blimps/aerostats, though.
 * Jupiter

The oldest and most hospitable Jovian colony with the most established government. Population generally anti-Koslovic but more moderate on the UN question than the Frieden movement at large; the Frieden never get a proper foothold until after the Jovian Moons Campaign. Could serve as the Jovian system's breadbasket?
 * Callisto

The vast majority of colonies are underground habitats bored deep into the ice to protect the inhabitants from Jupiter's radiation belt.
 * Ganymede

One of the Frieden's centers of activity. There are several local colonial governments, all of which are under the influence—if not direct control—of the Frieden movement in some way, e.g. being too intimidated by them or lacking in resources to stop them. Like on Ganymede, most colonies are subsurface warrens.
 * Europa

Smallest Jovian colony in terms of permanent population but has major mining activity.
 * Io

Various lesser moons and orbital stations/habitats - there was Koslovic activity on the minor moons, some of which were used to launch "workers' crusades" from; a few of the smaller moons were even destroyed in the wars.
 * Other

Saturn
Regarded as one of the most promising new frontiers of the system by this point, only a few of the moons are yet formally colonized, though the Frieden and various insurgent elements rapidly appropriated many of the lesser moons as hideouts and bases during their reign. Saturn is rapidly growing in importance as a strategic site due to the shallowness of its gravity well in comparison to Jupiter's and lack of an intense radiation belt, making it a coveted prize for all factions; however, the long travel times there limit its accessibility.

The most notable colony around Saturn. Mined for hydrocarbons (especially methane) and hydrogen along with various industrial operations. Due to its uniquely cold climate, Titan also serves as a budding hub of cutting-edge computing, AI research, and specialized industries, and several major corporations host data centers there.
 * Titan


 * Iapetus


 * Enceladus