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Battle of Leir III

Doisac campaign


the Great Schism


April 22, 2560 - July 28, 2560


Oth Sonin system (mainly Doisac and its moons).


Pyrrhic Sangheili victory

Sangheili coalition
Jiralhanae confederacy

86 warships

114 warships

"One way or another, this war will end on Doisac."
―Arbiter Thel 'Vadam to Coalition leaders.

The Doisac campaign—also called the Fall of Doisac—was a large battle fought between the Sangheili coalition and the Jiralhanae tribal confederacy from April 22 to July 28, 2560. It took place in the Oth Sonin system, primarily on Doisac, and was the final (and, perhaps, the most important) engagement of the conflict.



Since the fall of High Charity in 2552, the Sangheili and Jiralhanae have tirelessly fought one another in the brutal interspecies war known as the Great Schism. Years of exhaustive warfare did little to quell the hatred between the two species and yet, by 2559, after a string of stalemates and the pyrrhic outcomes, it became clear that the war could not last forever—the resources of both belligerents were drained to dangerous levels of sparsity and supplies were spread far too thin to carry on for much longer.

In early 2560, this predicament had been pondered upon considerably by Erebus, the self-proclaimed Chieftain of the Jiralhanae and leader of Covenant loyalists known collectively as the Jiralhanae confederacy. Knowing that the Elites were not much better off than the Brutes, he intended to gather the remainder of his forces and lead one final assault against the Sangheili where it would hurt most—their homeworld, Sanghelios. Under the utmost secrecy, Erebus sent out a call to all loyal chieftains and warlords across charted space to muster at Doisac, the Jiralhanae homeworld, where they would take time to grow in strength and then, together, make their move on Sanghelios.

Unbeknownst to Erebus, news of this plan would quickly reach Arbiter Thel 'Vadam and the Council of Kaidons thanks to the efforts of the Unggoy spy Jujum. While some on the council saw this as a cause for great concern, others saw it as an opportunity; for the first time since the war began, the Jiralhanae leadership would all be in one place, at one time. This was the perfect time to cut the head off of the Brutes and eliminate their will to fight. Like Erebus, Thel quickly began assembling a force that would journey to the Jiralhanae homeworld and crush the Brutes once and for all.

After a short period of gathering strength and reviewing intelligence reports on the Oth Sonin system's defenses, the invasion was underway. Due to the vast amount of assets and military commanders put at risk on both sides, it was evident to coalition leaders that this battle would decide the fate of the war and, ultimately, their species.


The N'goro Legion was instrumental in the Sangheili's subversion efforts.

Having been informed that Doisac possessed heavy counter-intrusion measures, Thel 'Vadam mobilized a small covert task force to undermine and weaken the opposition's defensive capabilities before the primary assault force entered Jiralhanae-controlled space.

Led by Yul 'Turul this task force, consisting of four stealth-capable ships, gained entry into the Oth Sonin system by performing a slipspace jump into the orbit of Jondum, a large gas giant. The radiation from Jondum disguised their drive signatures and the lack of luminaries in their ships allowed Tora's forces to evade detection from the Jiralhanae's simple tracking systems. Once there, 'Turul split the task force in two; the Assassin and Dagger were sent to Soirapt to disrupt operations at the local comms array and create an opening in planetary defenses, while the Surreptitious and his own ship—Equivocal Right—went to Teash to carry out the assassination of HVTs.

On Soirapt—a vital point to the Oth Sonin system's security network—elements of the N'goro SpecOps Legion were dispatched to seize control of the communications array, granting them access to and limited control of the entire star system's battle-net and sensor networks. With the relays, the SpecOps commandos were able to send fraudulent orders to a handful of shipmasters in the Brute fleet orbiting Doisac, fooling them into creating a hole in their defenses for the Sangheili. Meanwhile on Teash, 'Turul and Zealots of the Righteous Hand covertly assassinated an five Jiralhanae Alphas hunting in the colony's wilderness and began to sabotage garrisons soon afterward.

The coalition presence in the Oth Sonin system went unnoticed for a significant period of time, nearly nine hours, but suspicions finally began to grow when the Alphas on Teash didn't report for an important meeting of the war council. What's more, anomalies with ship movements and inconsistent naval orders also gained the attention of Vexus, the Fleet Master commanding Oth Sonin's entire defense fleet. Vexus dispatched a Type-52 Phantom to the comms array on Soirapt to investigate while also ordering the remaining troops on Teash to locate the lost Alphas. Though the Phantom was destroyed before it could report the subversion on Soirapt, Yul was convinced that the Brutes were now aware of there presence or would be very soon.

Intending to give the Brutes as little time as possible to prepare, Yul quickly sent the signal to the remainder of the coalition fleet that his force had been compromised; the time to attack was now.


Opening assault

A Jiralhanae battle-cluster over Doisac.

The battle for Doisac began with a rapid incursion as 80% of the Sangheili coalition fleet began jumping into the space around the planet, launching volleys of plasma torpedoes as they existed slipspace. The remaining 20% of the fleet, led by Resu Nar 'Yulvan, jumped into the orbit of Jondum where they would remain until signaled.

The sudden assault caught the Jiralhanae by total surprise, with many vessels being caught with their shields down and destroyed in the initial salvos. As coalition ships continued to appear simultaneously in numerous points across Doisac's outer-orbit, the Brutes were doubly disarrayed. The attack's expeditious nature coupled with the fact that they had only limited control of their own communications and sensor network and their own shock at the invasion made it initially difficult for the Brutes to put up any effective resistance against the attack. Confederate forces were essentially fighting blind, relying on their great numbers to fend off the invaders. Numbers, however, proved a disadvantage during this early chaos as many Brute ships, struggling to the avoid incoming fire, accidentally rammed their own allies; during these early stages of combat, just as many Brute ships fell to friendly-fire and error as to coalition forces.

To re-establish some semblance of coordination within the fleet, Vexus made the decision to deploy dozens of Liches carrying large communications nodes, transforming the spacecrafts into makeshift COMSATs; this way Vexus and the other naval leaders under his command were able to rally their forces and organize defensive lines more effectively. The coalition advance was slowed by the Brutes' increased coordination, but were not stalled entirely. The coalition bombardment, along with Seraph escorts, allowed dozens of boarding crafts to bypass the forward-most lines of the Jiralhanae defenses and insert troops into the larger destroyers, battlecruisers, and carriers at the back of the formations to destroy them from the inside with antimatter charges. Without support from the capital ships being lost or diverted the corvettes, light cruisers, and frigates continued to falter. By this point, both the assault carrier Ussa's Cunning and the brigantine Clarity made it through the lines to Doisac's surface, where the construction of cloaked landing zones began in both the Bediesh and Ull regions.

Jiralhanae counterattack

The naval battle left both fleets in tatters.

Vexus was confident in his ability to hold off the coalition fleet but the other Jiralhanae, both his subordinates and superiors, were not so sure. Hours after the initial battle erupted, Vexus' place as head of the fleet was revoked by Erebus, Chieftain of the Jiralhanae, who took up that position himself after boarding and assuming command of the Renegade. Shortly after his arrival, the Sangheili lost their slight strategic advantage as Erebus, a skilled naval tactician in his own right, coordinated his warships against the coalition aggressively and effectively.

Final space battle

Further engagements



Notable participants

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