The first 6 games are about World War II, but the series began branching out beginning with Modern Warfare. The series now spans World War II, the Cold War, the present, the near future, and the far future. The Modern Warfare series takes place in present times and is developed by Infinity Ward.

Vanguard's single-player campaign takes place in 1945 near the end of World War II's European theater, with various flashbacks ranging from 1941 to 1944. The story of Vanguard is told throughout various points in time in a non-chronological order.