Combat Mission: Beyond Overlord is a 2000 computer wargame developed and published by Big Time Software. It is a simulation of tactical land battles in World War II. Combat Mission began development at Big Time Software as Computer Squad Leader, an adaptation of the board wargame Advanced Squad Leader. It was set to be published by Avalon Hill. Big Time and Avalon parted ways shortly before the publisher's closure by Hasbro, and Big Time continued development independently, under the new title Combat Mission. Combat Mission was a commercial and critical hit, and began the Combat Mission series.