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War of Beginnings
During the war between the Sangheili and the San'Shyuum Reformists, First Kaidon Mhelaat 'Orlam, sought to change his species' stance on the application of Forerunner technology. Like their enemies, the Sangheili also worshipped the Forerunners as their gods, but they believed the direct physical application of their relics to be blasphemy of the highest degree and punishable by death. However, as the San'Shyuum and their powerful Dreadnought decimated colony after colony, 'Orlam saw the utilization of Forerunner technology—specifically their weapons—as the species' only hope for survival. Despite their dire situation, the Sangheili people resisted the First Kaidon's proposition, and he was eventually assassinated in response.
There were some Sangheili who agreed with 'Orlam, and a group of scientists began to secretly study their relics, incorporating their findings into warship, weapon, and armor designs. Eventually, these scientists emerged and professed their sins. Around the same time, 'Orlam's son, Pelahsar the Strident, proved the viability of reverse-engineered Forerunner weaponry with the successful test of the Reckless Pursuit, a modified R'sikosh-pattern man o' war. This, along with the worsening trend of the war, led the Sangheili to amend their beliefs; the scientists that had secretly researched Forerunner weaponry were also granted amnesty.
Formation of the Covenant
When the San'Shyuum brazenly assaulted Sanghelios and its two moons toward the end of the war, the Reckless Pursuit's weapons would prove enough to shoot down the Dreadnought, causing it to crash on Suban. While the vessel was held in place with gravity anchors, a coup resulted in the assassination of the Reformists' leader, Pervading Stone. This prophet was the main driving force behind his species' aggression, and with him gone, their new leader, Breaking Shadow, sent an unarmed delegation to the Sangheili in 852 BCE and presented the possibility of peace. Pelahsar the Strident, the newly-appointed First Kaidon, met with Breaking Shadow and a tenuous truce was formed, with both leaders forgiving each other's species for their crimes. This truce was soon formalized in the Writ of Union, the founding document of the Covenant.
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