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Subject 386, also known as the Groombridge Subject, was a Sangheili prisoner of war who was interrogated by Admiral Preston Cole, First Lieutenant Richard Barclay, and Solipsil. It was from Subject 386 that the United Nations Space Command first learned why the Covenant were systematically exterminating humanity. The interrogation of Subject 386 was what convinced Admiral Cole of the necessity of keeping Earth and the remaining colonies hidden, which eventually became the Cole Protocol.
Because "Subject 386" is the human designation for this Sangheili, its real name, gender, and rank are unknown, although it is presumed to be male due to the fact that female Sangheili have as far never been seen by humans. When asked its name, the Sangheili responded with a word that could not be translated, then told them humans were unworthy to hear it.
On December 24, 2530, the Sangheili was stationed aboard a Covenant assault carrier at the Battle of the Great Bear. When its allies were destroyed in orbit, the carrier attempted to flee but was shot down. It subsequently crash-landed on the surface of Groombridge-1830 in the city of Waterford, Lemuria. At approximately 1805 hours, the Sangheili was found alive in an enclosed compartment by two UNSC strike teams, who captured it and brought it aboard the UNSC Everest.
The following day, at 0240 hours, it was interrogated by Admiral Cole, with the Everest's AI Solipsil recording it and Lieutenant Barclay of the Office of Naval Intelligence holding the alien at gunpoint. Cole first asked its name and if it could understand him, but the Sangheili's words could not be translated. Eventually its words became discernible, and it expressed little fear of Cole's threats or death.
The interrogation was consisted of four excerpts, and lasted for 77 minutes. Cole asked it many questions, relating to why the Covenant was attacking humanity and why they struck Groombridge. The Sangheili told them that Groombridge was just another world, like all the others they attacked. When asked why they were attacked, the Elite's tone grew hateful, telling them humanity was like swarming maggots who were ignorantly desecrating the treasures of the ancients.
In response to the alien's boasts, Cole retorted that humanity had destroyed the Covenant fleet in the battle yesterday. The Sangheili scoffed at this remark, informing that three ships was hardly a loss for their enormous empire, especially when the humans had lost far more to destroy them. As the tone of the interview turned more violent, the Sangheili's heart rate increased and it started pulling at its restraints. Lt. Barclay brandished his gun at the alien, threatening to shoot it, but the Sangheili continued with its xenophobic rant. Its fervor began pulling it into cardiac arrest which, coupled with its injuries from the crash, led to its vitals flatlining from the strain. At 0417 hours on December 25, 2530, Subject 386 was pronounced dead and due to human unfamiliarity with its anatomy it was not resuscitated.
Cole discerned several clues from Subject 386, which he wrote of to his peer Admiral Michael Stanforth. Firstly, he determined that safeguarding Earth had to become the fleet's highest priority, as the Elite had spoken of the Covenant's desire to wipe out their species, not just defeat them. However, Cole didn't understand why the Covenant didn't know where Earth was, despite all their advanced technology. He suspected some conflict in the Covenant hierarchy might be keeping it from being found, and thus humanity needed to capitalize on this weakness. To give the hegemony no chance at uncovering the secret, Cole wrote a series of directives for the UNSC fleet to minimize their trail to other colonies. These directives were reviewed by ONI and implemented as official policy, becoming dubbed "the Cole Protocol".
However, the interview had left other mysteries. Cole had no answer as to why the Covenant were attacking humanity. 386's response had been mostly xenophobic rhetoric with vague reasons for the Covenant's hatred. Cole suggested theories such as humans being perceived as religious aggressors or that Earth might hold some kind of alien significance to them. However, he admitted he couldn't discern much more without further information, and he would not be able to defeat the Covenant for long the less he knew about them.
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