We embarked on a defensive war in 2001, and 4 years later we are winning. There have been no terrorist attacks on American soil since 9/11, and the global war on terror is confined to the theaters where we have chosen to fight it.
I'd quibble with the phrase "defensive war," because we've been on the offensive tactically since Afghanistan (Oct, 2001) and strategically since Iraq (March, 2003). But that's my only quibble. Go read the whole thing already.