2001 - 2002
In the aftermath of 9/11, the United States and its allies invade Afghanistan for the beginning of a decades-long stay.  Al Qaeda and the Taliban are decisively routed in a matter of weeks, but Osama bin Laden manages to give the U.S. military the slip at Tora Bora.  
Meanwhile, the United States and other countries around the world begin to face new security challenges, from the outside as well as within.