The first Call of Duty game was released in 2003. Developed by Infinity Ward and published by Activision, it launched for Microsoft Windows on October 29, 2003.
The game was designed as a World War II first-person shooter and drew comparisons with the Medal of Honor series. Its campaign was distinctive because it presented the conflict through American, British, and Soviet perspectives rather than following only one soldier or army.
Players sometimes confuse the original release with Call of Duty 2, which arrived in 2005, or Call of Duty 3, released in 2006. Those were later main-series installments. The original title was simply called Call of Duty, without a number or subtitle.
Infinity Ward built the game using a modified version of the id Tech 3 engine, the technology associated with Quake III Arena. Its success established the franchise and led to a long-running series of sequels, spin-offs, and annual releases.