From Halopedia, the Halo wiki
Edgar Sykes was a member of the UNSC Navy. He was a lifer, meaning that he had re-enlisted to his position at least once. He was a good-humored man (although he enjoyed annoying Jacob Keyes good-naturedly) and kept up the morale of those around him. In 2535, he was assigned to the UNSC Destroyer UNSC Armageddon's Edge when it traveled to Chi Rho in the Ectanus 45 system. During this assignment, he was in his mid-fifties. 
While his rank was never explicitly stated, he was described as the "on-duty officer" of the Armageddon's Edge and he was able to openly (though good-naturedly) make fun of Keyes' rank of Lieutenant, implying that he was the Captain of the ship.
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