Doisac campaign

The Doisac Campaign was the largest and final engagement of the, which pitted the and  against one another on the Jiralhanae homeworld of.

Though both sides sustained heavy casualties, the Loyalists were ultimately defeated -- losing not only the battle, but the war as well.

Background
Though the war between the Sangheili and Jiralhanae raged on into the 2560s, it was clear from the heavy toll being taken on both sides that the conflict would soon come to a bloody end.

When the San 'Shyuum disappeared into hiding, leadership of the Covenant Loyalists fell to the Alpha Tribes, the governing bodies of the Jiralhanae. Though there were few Alpha Chieftains in 2560 still in the Covenant -- most either being dead or forming their own splinter factions apart from the Covenant -- they still managed to form an effective administration over the Covenant, through fear more than faith.

The Alpha Chieftains, who were once scattered across Covenant territory by order of the Prophets, had now migrated themselves as well as vast military assets to the Oth Sonin system, specifically Doisac and its moons. It didn't take long for Seperatist intelligence to learn of this migration of the Covenant's leadership. Though Doisac was the homeworld of the Jiralhanae, it was strategically unimportant for most of the Great Schism as the Loyalist leadership and military might were largely deployed in other parts of the Orion Arm. With the Alpha Tribes now in one place, the Separatists only needed to deliver a single devastating blow to crush the military strength and leadership of the Loyalists.

The Sangheili spent months gathering intelligence on Doisac's defenses, looking for any and all weaknesses to exploit. They quickly developed their invasion plans and began mustering the resources necessary to carry out their assault, finally achieving a favorable military force in 2561 which would be commanded by Thel 'Vadam, himself.

Going into the battle, it was clear to Thel that no matter who was victorious in the battle, the large amount of assets put at risk on both sides meant that it would be the final engagement of the war.

Pre-Invasion Operation
Knowing that Doisac possessed heavy counter-invasion measures, Thel 'Vadam mobilized a pre-invasion task force to covertly soften their defensive capabilities.

Led by the Tora 'Kivam, this task force -- comprised of only eleven vessels -- entered the oth Sonin system by making a slipspace jump into the orbit of Jondum, a gas giant. The radiation from Jondum effectively disguised their slipspace signatures and the lack of luminaries in their ships allowed Tora's force to evade detection by the Loyalist's rudimentary tracking system.

After entering the system, Tora split his task force apart. Sending the assault carrier Stalwart and the corvettes Surreptitious and Equivocal Right to Solrapt, he hoped to quickly disrupt communications and punch a hole in their planetary defenses.

After the Stalwart and its corvette escort arrived on Solrapt -- a vital part to the Oth Sonin system's security network -- it began constructing a cloaked landing zone where it could hide on the planet. The corvettes began deploying strike teams from the N'goro Special Operations Legion to launch covert attacks on communications relays and take control of them, effectively hiding evidence of the strike while giving them limited control of the Loyalist's communications and sensory array.

The N'goro SpecOps commandos used the relays to sent fradulent orders to a handful of ships in the Loyalist fleet orbiting Doisac, effectively fooling the ships into creating an opening in their defenses for the Seperatists. Tora took advantage, moving his flagship -- the Resolution -- with an escort of two CCS-class battlecruisers through the opening and into one of Doisac's many deserts. There, construction on a second cloaked staging ground began.

The remaining five battlecruisers in Tora's task force, backed by squadrons of Seraphs and banshee Fighters, began methodically picking off small patrols in the system.

The Seperatist's presence in the Oth Sonin system went unnoticed for a surprisingly long time, nearly six hours, but suspition began to grow when contact with various ships were lost. Vexus -- commander of Doisac's entire defense fleet -- was the first to notice the anomalies. With the no longer around, it was common for their equipment to make incorrect readings or outright break, but never before had communications with dozens of ships been lost at a time. He also noticed inconsistencies in data retrieved from various warships, whom were given orders that he didn't authorize.

Vexus quickly sent the corvette Zealot to investigate the communications outposts on Solrapt to see what the issue was. The Zealot, led by Shipmaster Oenimus, arrived in the orbit of Solrapt within an hour where it was quickly destroyed by the Stalwart.

Convinced that the Loyalists now knew of their presence in the system, the task force sent a message to the rest of the Seperatist armada -- the Combined Fleet of Indignation: it was time to attack.

Opening Engagement
The battle for Doisac began rapidly. Believing the Loyalists had already discovered the presence of their pre-invasion force in their system, the Separatist armada began pouring into Doisac's orbit, firing plasma torpedoes as they entered real-space.

The Sangheili had no idea that they'd caught the Jiralhanae by complete surprise, but their quick realization of this fact led to a more coordinated attack rather than blindly firing on their adversaries.

The Separatist armada did not appear all in one single position over Doisac but rather, the entire fleet appeared in pockets around the globe. The fact that this attack was quickly occuring all over the planet simultaneously while the Loyalists had only limited control of their own communications network in the system made it initially difficult to coordinate an effective defense against the Sangheili. The Loyalist forces was essentially fighting blind, fending off the Sangheili with sheer size and ferocity alone.

To help even the odds and re-establish communications with the rest of his armada, Vexus made the decision to deploy carrying large communications nodes, effectively transforming the ships into makeshift COMSATs. This way, Vexus and the other naval leaders under his command -- who had grown to be far more strategically saavy than they had been in the past -- were capable of coordinating a more effective defense against the Separatist armada, leading to the odds tipping back in favor of the Jiralhanae.

Neither Thel 'Vadam nor Vexus led their armadas at the head but rather, their flagships rested in naval formations known as 'core fleets' -- the primary command formation of a given fleet.

Vexus' core fleet took position behind the bulk of his defensive line, while Thel's core fleet took position within the center of numerous other ship clusters, remaining relatively far-flung from Doisac's primary defenses in an attempt to study his enemy's movements since the Loyalists defensing Doisac were apparently employing tactics different from anything the Separatists encountered prior.

Sixteen hours after the initial engagement between Sangheili and Jiralhanae forces erupted, 60% of all ships in battle over Doisac were centralized at a singular point in Doisac's orbit over the continent of Kethal with the remainder clashing in places from Doisac's orbit all the way out to Warial, the planet's farthest-flung moon.

Vexus noticed that most of Thel's ships were nearly firing on his forces, but not making any attempt at advancing on his fleet. This made the Alpha Chieftain grow bold, and he emerged from behind his armada, backed by an intimidating number of destroyers and cruisers.

Thel saw this and withdrew numerous ships back, causing Vexus and many other ships advance and prepare to fend off the invaders. As Thel and a cluster of numerous ships retreated further and further from Doisac's primary defense zone, Vexus and nearly 60 ships continued to advance.

While Vexus began to believe he had the upper hand, it was a feint. Thel eventually stopped his retreat and instantly following so, numerous Separatist destroyers and assault carriers appeared from slipspace and the flanks of Vexus' forces. All at once, Thel and his ships bombarded the Loyalist core fleet and the ships that surrounded it, destroying many of them and forcing Vexus into a narrow and hasty retreat back to Doisac's main defense line.

By this time, Thel had finished prodding at Doisac's defenses and devoted the majority of his armada to engage and destroy the Loyalist fleet. Vexus, thrown off and angered by the fact that he'd allowed himself to be drawn into a trap, retreated to the rear of his armada and began coordinating his forces to the best of his ability.

The battle for naval supremacy would continue for the next several weeks, encompassing the entirety of Doisac's orbit once again.

Continued Naval Action
Following the initial assault of the Loyalist defense array, the battle between the Sangheili and Jiralhanae continued to intensify. Weeks of conflict and loss on both sides culminated into the creation of a massive debris field forming over Doisac, significantly changing the battlefield and adding a new element of strategy to the engagement.