Lieutenant Commander Xaing Cho is a UNSC senior officer and chief engineer aboard the UNSC Dusk. He was technically past the mandatory retirement age for the UNSC Prowler Corps, which was quietly ignored by his commander, Captain Iglesias, as Cho is an extremely skilled engineer and impossible to replace.
Cho was at his post in 2552 during the Battle of Earth. Commander Richard Lash took the ship into Slipspace in pursuit of the High Prophet of Regret's Assault Carrier which was being pursued by the UNSC In Amber Clad. Cho stayed at his post on the trip to Installation 05, back to Earth, to Onyx and the Battle of Onyx, and then back to Earth again.