War of Many Banners

The War of Many Banners was a multi-faction, interstellar conflict that took place across Sangheili space roughly between 995 BCE and 970 BCE. It was primarily fought between the Crimson League, Thar'shi Sphere, and Nirphal Resurgence; several other far smaller factions also participated in the war. The intensity and scale of the fighting ebbed and flowed over its duration.

The Sangheili's final large-scale civil conflict before the War of Beginnings and the creation of the Covenant, the War of Many Banners saw the formation of the political blocs that would, soon after, face the San'Shyuum.

Background
The War of Many Banners was set against the backdrop of what would later be broadly known as the Ages of Strife, a period of cold and hot war between several of the political blocs within the Sangheili sphere. During this time, tensions rose between the Crimson League and the Thar'shi Sphere, which became the two largest powers in the Urs system. These polities sponsored several proxy wars in the Urs system and beyond, backing opposing rebel groups and lesser clans. The Thar'shi Sphere notably backed the Nirphalite movement among the Voidborn, the spacefaring populations of the Urs system, who would several decades later come to declare the Nirphal Resurgence and challenge both major factions.

The debate over Suban
A long-running debate over claims to the moon of Suban played a large role in sparking the hostilities. Strategically vital for its natural resources, most notably the Subanese crystals, and its location atop Sanghelios' gravity well, control over Suban was a prize coveted by the spacefaring powers of Sanghelios. Suban was originally settled centuries earlier, before the Skyfall, and due to the consequent dark age, records of the moon's first colonists were scarce. Suban's population became divided during the dark age, and these rifts grew even greater as the tensions of the Ages of Strife mounted. The Thar'shi Sphere and the Crimson League supported opposing sides among the moon's increasingly polarized population. The Thar'shi Sphere held that their ancestors, the Kharsim ethnic group, had settled Suban as a penal colony, a story corroborated by the folklore of the pro-Thar'shi segment of the Subanite population. However, several populations of what would become the Crimson League also had credible claims to parts of the moon, as well as a large support base among the populace. These were not the only factions on the moon; another prominent movement, the Sentinels of Miatistina, campaigned for a pan-Subanite alliance and detested any attempts by Sanghelios to influence the moon's affairs. While the Subanite Brotherhood was formally neutral thanks to impartiality pacts from ages past, their support of the Sentinels of Miatistina was widely known.

Skirmishes over Sanghelios
Fighting between the Crimson League and Thar'shi Sphere broke out around Suban proper in 995 BCE. This conflict was initially limited to the moon itself, as neither side wanted to escalate and risk other holdings or their heartlands on Sanghelios. This off-and-on skirmish lasted for several years as neither side gained much ground. For the most part, local forces of both factions did the brunt of the fighting. As time wore on, both factions began to face the dire prospect of force depletion and the requirement of forces from other corners of each empire.

The conflict escalated once more when the Thar'shi Sphere targeted one of the Crimson League's suppliers, the Merchants of Qikost, on the other moon of Sanghelios. Thus beginning the protracted Siege of Qikost.

The Nirphal Resurgence
Amid the fighting, several colonies and vassals from both factions attempted to secede and form a loose coalition known as the Nirphal Resurgence. This was a movement largely based around the colonies orbiting the red dwarf Joori, whose populations still harbored grudges going back to the Joorian Reconquests. Several affiliated minor colonies within the Urs system as well as Joorian-sympathetic interstellar colonies would join the resurgent Nirphal cause, which found some supporters even on Sanghelios proper. The movement began organically but eventually was given materiel, logistical, and training assistance by the extra-Ursian Irshun League.

By the 980s BCE, the Nirphal Resurgence confronted the Crimson League in several places in the Urs system. Fighting between the Thar'shi and Crimson League died down briefly as both factions pivoted to confront the uprisings and attacks. Extensive campaigns in the Arodan system also took place.

Resumption of fighting
Although intermittent fighting with the Nirphal Resurgence continued, the primary two factions turned their sights back to each other once more. Fighting at proper interstellar scale was in full swing. Battles took place at Korisphol and Troystrada.

Back at Sanghelios, strikes of territories on the planet were common by this point. Crimson League forces had mostly annexed Thar'shi Subanite territories by this point, creating further contention with the Sentinels of Miatistina and the Subanite Brotherhood. Fearing a new guerrilla campaign with the Miatistina through Subanite Brotherhood lands, the Crimson League would establish de facto military control over the Subnite Brotherhood's territory.

Silver Beacon Treaty
The fighting came to an end with the signing of the Silver Beacon Treaty at Korisphol. The Treaty passed Suban decisively into the Crimson League's sphere of influence, not only with the annexation of Thar'shi Subanite territory but with the suzerainty of the Subanite Brotherhood. The two additionally contested colonies of Yervun and Lhiaron respectively, were given to the Crimson League as well.

Most of the colonies closer to Urs which joined the Nirphal Resurgence were folded back into their respective factions. The most hard-to-reach colonies were allowed independence due to the vast distances at the time. Some of these independent colonies would join the Irshun League later on.

Legacy and prelude to the War of Beginnings
The War of Many Banners was significant in many ways. The conflict and its accompanying arms race saw various steps toward the paradigms of technology, strategy, and tactics that would dominate Sangheili doctrine at the start of the War of Beginnings.

With the defeat, the Thar'shi Sphere eventually turned outward from the Urs system and focused more of their efforts on expanding their empire through colonization and conquest. This would in part lead to the colonization of Ulgethon, the site of the first battle in the War of Beginnings.