'Time to end the Forever War' -Biden

"We were attacked. We went to war with clear goals. We achieved those objectives." Biden said.

In his White House speech, Biden set a goal of withdrawing all 2,500 U.S. troops remaining in Afghanistan by Sept. 11.

By pulling out without a clear victory, the United States opens itself to criticism that a withdrawal represents a de facto admission of failure for American military strategy.

Biden said critics who say the U.S. will only meet its diplomatic goals in Afghanistan with a robust troop presence haven't learned the lesson of history.

"We gave that argument a decade," he said. "It's never proved effective. Not when we had ninety-eight thousand troops in Afghanistan, and not when we're down to a few thousand."