Changes
=== Call of Duty 1 ===
This was the original game, released in 2003. It was developed by Infinity War, and it was set in WWII, following Allied paratroopers into the heart of the battle.
=== Call of Duty 2 ===
=== Call of Duty 3 ===
This game is still another WWII FPS game, and it was developed by Treyarch and released in 2006. This was the first game to also be released on other platforms, including PS2, PS3, Wii, XBox, and the Xbox 360. This game is still set in WWII, but now also follows the Canadians, Polish, and the French armies after D-Day.
=== Call of Duty: Modern Warfare 2 ===