The World at War maps were ported over in the Hardened and Prestige versions of Call of Duty: Black Ops, and feature Black Ops cold war weapons as well as some of the original World at War weapons (e.g. Kar98k, Thompson, FG42, etc.). The Rezurrection DLC made the World at War maps available for purchase.
Call of Duty: Black Ops is the seventh installment in the series, the third developed by Treyarch and was published by Activision for release on November 9, 2010. It is the first game in the series to take place during the Cold War and also takes place partially in the Vietnam War.
