Modern Warfare

The idea of a 'Modern Warfare' theme for Call of Duty 4 was probably to move the series in a new direction as well as give the player a different variety of weapons and environments to fight in.

The change of time-period was not without it's drawbacks however. The enemies in previous Call of Duty games had always been the axis powers, Nazi Germany, Fascist Italy, etc. But in the modern age, there are no distinct enemy nations of the U.S. or U.K., so a new, fictitious group known as the Ultranationalists was invented.

The Ultranationalists were essentially a combination of two things, Russian Communists, and Islamic Terrorist Extremists. However, how it is that a group of such well-organized and well-equipped Middle Eastern Terrorists (surprisingly none of which are suicide-bombers or users of guerilla warfare tactics) came to be so friendly with a group of Communists (which is a form of government that is absolutely despised by the Middle-East) or even came into being is never explained. But then, the alternative must have been for Infinity Ward to have the game take place in Iraq... which would have been a taboo move for many obvious reasons.