Battlegroup Stalingrad was comprised of nine ships and commanded by the late Admiral Carl Patterson. Its flagship was the UNSC Stalingrad, a UNSC carrier. In 2552, the battle group was deployed to Onyx to retrieve Dr. Halsey, a joint unit of SPARTAN-IIs and SPARTAN-IIIs, and (supposedly) examples of Forerunner technologies that had been excavated and recovered.