Which Counter-Strike game introduced the multiplayer mode called War Games?

Counter-Strike: Global Offensive introduced the multiplayer mode called War Games. War Games grouped alternative rule sets that changed the usual Counter-Strike format, including modes such as Arms Race, Demolition, and Flying Scoutsman.

These modes were designed for shorter or more experimental matches than standard competitive bomb-defusal and hostage-rescue games. Arms Race, for example, gives players a progression of weapons after eliminations, while Demolition combines rounds with weapon progression and bombsite objectives. Flying Scoutsman changes movement and gravity while centering play around the SSG 08.

War Games should not be confused with Danger Zone, the battle-royale mode introduced later in Global Offensive. It is also separate from Casual and Competitive matchmaking. The name describes a category of alternate multiplayer experiences rather than one single ruleset.