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- “You need to do more than overthrow the Arbiter. You need to wipe both him and Vadam from the face of Sangheilos, because as long as that state exists, it will remain loyal to him, and it will exert its power and influence.”— Shipmaster Buran 'Utaral to Avu Med 'Telcam.
The seeds of the Sangheili Civil War began immediately after the end of the Great Schism and the Human-Covenant war. In January 2553, the Arbiter Thel 'Vadam began to visit the various states to propose a peace treaty with humanity. He argued that too many Sangheili had been lost in the Great Schism, and that Sanghelios had to be rebuilt. This proposal was not well received by all, and civil unrest ensued. Dissident Sangheili began to join the Servants of the Abiding Truth, an old orthodox religious group who opposed the Arbiter led by Avu Med 'Telcam.
In February 2553, Fleet Admiral Terrence Hood arrived on Sanghelios to formalize the cease-fire with the Arbiter. They met in the state of Vadam and formally ended hostilities, solidifying the Treaty of 2552.
In 2553, the United Nations Space Command's Office of Naval Intelligence, with the help of a civilian consultant named Evan Phillips, made contact with Avu Med 'Telcam. They agreed to arm them with Sangheili weapons in exchange for the Servants leaving humanity alone if they seized power. ONI's true goal was to keep the Sangheili administrative and military authorities weak and disorganized until humanity could rearm and eliminate the Sangheili race altogether.
Outbreak of the battleEdit
After a Jiralhanae uprising in Ontom, right outside the Servants' headquarters, 'Telcam decided the time had come to begin the rebellion. He and his supporters gathered their ships, vehicles and troops and attacked Vadam. The Arbiter was winning at first, since fewer keeps joined the rebellion than 'Telcam had thought, with two of 'Telcam's ships being shot down early in the battle, including the Unflinching Resolve. The tide turned when the Arbiter allowed Kilo-Five to land on Sanghelios to search for Evan Phillips in the Temple of Abiding Truth. Many Sangheili viewed this as a desecration and joined 'Telcam's side. The Servants quickly surrounded Vadam Keep and began a siege. The tide turned once more when Admiral Hood arrived in orbit with the UNSC Infinity and offered the Arbiter aid, which he grudgingly accepted. The Infinity shot down 'Telcam's ship Defender of Faith and fired a MAC round directly into the besieging forces outside Vadam Keep. The siege quickly became a rout as the Arbiter counter-attacked. 'Telcam and the Servants were able to retreat to four frigates and proceeded to escape from the planet with five of the Arbiter's cruisers in pursuit. At this point Captain Serin Osman was forced to protect the escaping frigates from the Arbiter's fleet, spoofing her ship's signal to register as a Kig-Yar vessel. Osman managed to destroy three of the Arbiter's cruisers with Nukes, the Devotion, Far Vision and Axiom, but one of the remaining cruisers, the Swordsman, managed to shoot down the Cleansing Truth. The three remaining frigates managed to escape intact, along with all the troops, vehicles and supplies the ships could hold, to New Llanelli. The rebellion was crushed for the time being, and the Arbiter remained in power on Sanghelios, however in a weakened state.