US-RU War (Modern Warfare 2)

The United States - Russian War began in 2016, when following a supposed US-funded terrorist attack, Russia led a surprise invasion of the East Coast (and possibly West Coast). The war led to the Battle of Washington.

Background
The war was kicked off by the events of No Russian, when Allen's body was found amongst those of Makarovs gang. Leading to the Russian public to believe the attack was funded and operated by the US goverment (which is technically true, considering Shepard does work for the goverment). Soon the Russian public demanded a counter attack and the Ultranationalist Party was happy to do so. The Russians, having cracked the ACS module, were able to mess up Americans defense system and so began the war.

The Invasion
The Russians using the cover of a glitched defense system were able to land on the Eastern seaboard with little resistance. (It is also possible a second invasion of the West coast was happening simultaneously). They were able to reach at least as far as Washington before they are believed to have met any American military forces.