M723 Kangaroo

The M723 infantry support vehicle, nicknamed the Kangaroo or simply the Roo, is an infantry fighting vehicle in service of the UNSC Marine Corps.

Role
As the more aggressive counterpart to armored personnel carriers such as the, the M723 Kangaroo is envisioned as a vital supporting pillar of UNSC Marine assaults. They are used as transports, carrying up to two fireteams as close to the battle as possible, often using their superior speed to evade enemy barrages. They then complement Marines by directly targeting fortified emplacements and attack craft that would normally be able to cut them down, and creating openings with suppressive fire. Once the initial advance has been successful, Kangaroos transition into full-fledged infantry support assets, where their impressive countermeasures, scanning systems, and most of all their secure communications array keeps team leaders connected to the Battlenet.

Outside of this, Kangaroos are also used as escorts for convoys, where it is feared that the much lighter Warthog is insufficient for protection, yet speed is still required. They may be used as transports themselves, but the limited interior space compared to existing vehicles does not make it useful in this role. However, their advanced mapping suite, communications array, and high speed meant that they enjoyed use as a heavy scout in occupied regions.

Weaknesses and counter-tactics
The Kangaroo's main weakness is its low endurance. In combat, it has been found that its onboard supply of rockets is woefully insufficient for any protracted engagement, requiring it to be replenished either in the field or return to base far earlier than its 700 kilometer range would suggest. More munitions could be carried within the troop bay, but this creates a risk of creating mass-casualties if the armor is breached. Early vehicles also suffered from a design defect in their drivetrain that created strange vibrations that drastically raised its fuel consumption at high speeds, and there were concerns that the added stress would lead to the shafts snapping at some point. These problems have since been rectified.

Development
The vehicle that would become the M723 Kangaroo was not originally developed for the UNSC, and indeed, it almost missed out on service in that organization. It was instead designed for the small Private Military Corporation known as the Grey Guard, whose lack of Pelican dropships meant that they could not use traditional surplus APCs such as the Bison. As a result, they negotiated with the Garrido Compañía de Motor (GCM) on Midvale for a specialized fighting vehicle that was compact and well-armed for its size, better protected than the Warthog but light enough to be carried on the commercial fliers the Guard employed. Here, they enjoyed enough success to justify continue more widespread production, but they remained fairly obscure for many years.

GCM initially attempted to offer it to the Colonial Military Administration, who declined on the account that they had no need for it. In 2504, they instead submitted it to the UNSC Marine Corps, who were hosting a design competition for a new infantry fighting vehicle to support fireteams in urban environments. The lobbying by far larger corporations meant that it was difficult for GCM's submission to be tried fairly, and indeed, it was almost dismissed on two occasions. Fortunately, pragmatism prevailed and two years later, the UNSC announced that the Kangaroo was the winner of the contract. However, GCM did not have the facilities that could match the numbers demanded by their new customers; instead, Chalybs Defense Solutions were subcontracted to manufacture the vast majority of the new IFVs.

Armament
The primary armament of the M723 Kangaroo lies in four M101 recoilless rifles, which are chambered for 120x508mm rockets or missiles. Each launcher is able to fire 14-15 times per minute, for a total barrage of 60 rockets launched across all four cannons in the same time frame. The turret is on an elevating platform, which allows it to be sunk somewhat deeper into the vehicle to decrease its target profile while moving, and extend the turret's traverse from 10 degrees to 45 degrees escalating. Although disembarking is possible while the turret is lowered, the low ceiling clearance makes this an uncomfortable affair. In situational cases, such as when the regular munitions are not available, the barrels can be replaced with 102mm bores so they can also use the M19 missiles issued to UNSC Marines.

The M24 120x508mm missiles used by the Kangaroo are usually equipped with high explosive, anti-tank warheads, which were incredibly effective at entrenched opponents, larger armored vehicles, and even groups of massed infantry. Main battle tanks such as the M808 Scorpion required repeated hits for their armor to be breached, but lighter, less combat-oriented vehicles could be destroyed or disabled in a single hit. However, an assortment of other warheads can be carried, such as high-velocity rockets for use at short-ranges.

To protect it against infantry, as well as offer further suppressive fire capabilities, two pintle turret hardpoints are fitted on each side of the Kangaroo. These are open-seated positions, similar to that on the M808C Scorpion, and what weapons are fitted are strongly informed by mission requirements. Most commonly, the M247H machine gun is typically fitted, which is chambered for 12.7mm .50 cal rounds and is used for anti-infantry defense. Another common choice is the M460 automatic grenade launcher, which fires 40mm timed or trigger-linked explosives at aggressors. Although primarily intended for use against vehicles and as indirect fire support, the M460's grenades can release a strong EMP that can significantly damage shields or temporarily cut power to generators and vehicles. A hybrid combination of both weapons is not uncommon, but only the grenade launcher is able to fire at both sides of the Kangaroo. The pintle mounts originally came with gunshields, but during the Human-Covenant War, the costs with replacing them meant that they became rare sights in the latter years of the conflict. In place of these, the gunners typically jury-rigged two M41 rocket launchers to each side for an immediate increase in firepower, despite the newly-introduced risk of detonation if they are hit by plasma fire.

In some variants, the Marines carried aboard may have access to armored gunports, which allows them to use their firearms to directly complement the Kangaroo's firepower. However, this is not a universal upgrade, as the gaps makes the vehicle's armor more likely to crack and break apart. In addition, it also makes them vulnerable to chemical weapons.

Defenses and Countermeasures
To protect it from incoming fire, the M723 Kangaroo is plated with between 8 and 17mm of composite plating, which mixes titanium alloy with graphene-ceramic plates to keep the armor strong without making it brittle. Some plates, such as the armor skirting, are suspended from the hull on hydraulic supports. These are connected to the impact warning system, and can move or adjust the angle of the armor to defeat kinetic penetrators and HEAT warheads, where it is hoped that they would either bounce over or down into the ground. Although not always fitted, Valiant non-explosive reactive armor is sometimes fitted to the sides and front of the vehicle to protect it from anti-tank weapons.

For its size, the Kangaroo is considered best-in-class in terms of active countermeasures. A pair of countermeasure dispensers are fitted, which launch flares, smoke canisters, and anti-munition missiles to draw off incoming missiles and hostile fire. This is bolstered by an onboard multispectrum dazzler array, which can be directed to either blind unprotected men (for permanent or temporary duration), or confuse guided missiles used against it. A sizable communications jamming array is fitted to hinder enemy coordination, which when linked to a larger communications dish, allows UNSC troops to punch through battlefield interference and continue to operate cohesively. The external ammunition dumps can even be used for carrying drones for self-defense purposes, although at the time of its introduction, the UNSC had few compatible models to use it with. Passive defense systems include the standard anti-mine suite, which can detect buried explosives in a small radius around the vehicle. A sensibly-organized EMP shield is integrated within the hull of the Kangaroo, which protects the delicate electronics within.

Crew and complement
Under ideal conditions, the Kangaroo is designed with a team of five in mind: one driver, three gunners, and the commander. The driver sits directly in front of the main gunner in the cockpit, which is offset to help alleviate the issues involved in transitioning from other tanks and vehicles. These seats extend back to allow for easy access. The commander is given their own station on the right side, and has access to all countermeasure arrays and optical cameras needed to coordinate the crew. While a single serviceperson with a neural interface is capable of piloting, firing the autocannons, and use the defensive systems on their own, a larger crew means that repairs can be conducted in a much shorter span of time. However, during the Human-Covenant War, the risk of losing so many people when one of these vehicles are destroyed meant that this advantage is often disregarded.

For transportation, two padded bench seats line the sides of the Kangaroo's interior, each of which has space for three UNSC Marines each. Another four are recommended to stand, which gives them a recommended complement of ten UNSC Marines. It is possible for fourteen or even fifteen troopers to be carried, although doing this makes it difficult to disembark in a timely manner. There are two doors on each side that slide open forwards to allow them to exit, although the much larger rear door is typically used. There are weapons and ammunition racks near the front of the Kangaroo, and the seats cover storage spaces. In emergency situations, these can be retooled as hospital beds for wounded.

Drivetrain
The Kangaroo is one of a growing number of vehicles fitted with a 6x6 suspension system, with each pair of wheels being able to turn independently of the others to reduce its turning radius. Furthermore, each wheel is able to pivot independently, to more easily climb travel over difficult terrain. The tires themselves are made out of a solid carbon nanotube webbing all through it, and the lack of need of an inflatable gas ensures that so long as the nanotube supports remain, punctures will not affect its ability to roll. The large tires are intended to be used with high-traction treading to resist getting stuck in off-road environments, although much lighter equivalents used for operation on roads are also available.

Two Traxus 99S heavy-duty motors provide power for movement. Normally, their design specifications only allows them to accelerate a vehicle as heavy as the Kangaroo up to just under 85 kilometers per hour, however, a third shaft connected up to a Dormant PU44R electric motor can overcharge this up to 120 kilometers per hour (75 mph) on a straight flat road. This can only be done for a short time, however, as the battery is rapidly depleted and requires charging from the hydrogen-powered 99S motors. While pure gas is recommended, as per UNSC recommendations, a sophisticated water electrolysis machine with suitable filtration is fitted,which allows any water source to be used as a potential fuel source if needed. If working in a toxic atmosphere, then the Oxygen is recycled to refill the air tanks.

Electronics
The M723 Kangaroo is an integral part of Marine communications, with a wide suite of options available to both team leaders and the regular grunt. All models are paired with a series of encrypted short-ranged receivers and transceivers suitable only for secure short-range chatter, meaning that unless the Kangaroo is destroyed, any UNSC Marine can communicate securely with their peers. This also rigs a false-chatter system to further dissuade attempts at decryption by providing incorrect information to the enemy, fed by a dedicated program.

For sensors, there is no short supply there either. Portable RADAR arrays constantly sweep the area around the vehicle for hostiles and friendly locations, while electro-periscopes gives the crew visual contact of the Kangaroo's blind-spots. There are stats used for furthering weather predictions, with humidity, wind speed and direction, time, and even the location of any orbiting moons being factored into its internal computer. A mapping suite is also built into the Kangaroo, which can use data retrieved from orbital satellites, any nearby drones, or Marine combat visors to create a detailed topography of the nearby areas. This can be edited by any officer with the appropriate clearance, so objectives, areas of interest, and identified obstacles and fortifications can be readily marked at any time.

The driver and gunner all have access to the standard heads-up display used by UNSC armored vehicles. A cursory view would see icons of UNSC troops (via their Infantry Friend-or-Foe tags), the projected firing arc of the Kangaroo's weapons, incoming weapons alerts, and detected sources of jamming. Although appearing cluttered to the untrained eye, it works seamlessly with their neural implants to organize the information when the operators desire it.

The Kangaroo is noted for its extreme resilience against electromagnetic pulses. Layers of faraday cages, redundant processors, and circuit-protection devices are all fitted to enable its computer network to withstand EMPs that exceed those generated by nuclear weapons. This is one of the aspects that have been over-engineered by GCM back when it was competing for the UNSC Marine Corps' contract, and remains by far the most expensive aspect of the vehicle.

M724 Tactical Command Vehicle
The M724 Tactical command vehicle is a modified version of the Kangaroo, in which most of the space used for transporting Marines is taken up by a command station manned by one or two officers. A much more reliable communications suite is fitted, complete with a Mark 47 ground-to-orbit communications dish, which can accommodate large amounts of traffic, defeat sophisticated jamming methods that it is likely to encounter in the field.

M746 Mobile Gun System
Introduced during the Human-Covenant War, the M746 Mobile Gun System, also known as the Cheetah, is one of several designs submitted for a formidable tank destroyer that exhibited retained impressive mobility, both of which were necessary for raids against the advancing Covenant armies prior to the main clash. In exchange for one of its pintle mounts and all of its Marine capacity, the Cheetah brings to bear a 120mm smoothbore high-velocity cannon, which is installed in an oversized turret to give the vehicle enough mass to absorb its recoil. It can also be equipped with 90mm, 105mm, and later 150mm bore barrels, with shell velocity and accuracy increasing as the bore diameter reduced. There is no increase in armor thickness, although a larger powerplant is installed to give it a maximum speed of 90 kph (56 mph).