A squadron of the Space Marine Corps, X-Ray Squad was part of Operation Alien Overlord in the Stroggos Campaign. The squad was transported by Coalition starship Phobos.
Marine Bitterman, one of the most celebrated heroes of the Strogg War, was a member of this squad. It is presumed the rest of the squad, including Sgt Boomer, were lost to the Strogg EMP defenses during planetfall.