The current strategic doctrine , which Defense Secretary Donald Rumsfeld issued in his Quadrennial Defense Review of early 2001 ( before the 9/11 attacks ) , is a package of U.S. military requirements known as 1-4-2-1 . The first 1 refers to defending the US homeland . The 4 refers to deterring hostilities in four key regions of the world . The 2 means the US armed forces must have the strength to win swiftly in two near-simultaneous conflicts in those regions . The final 1 means that the US forces must win one of those conflicts " decisively "
9/11 attacks
September 11 attacks
Military doctrine