Asked if he could define "victory" in the war in Afghanistan during a news conference, Obama said, "We can be successful in our mission, which is narrowly drawn" to ensure al-Qaida cannot attack the United States, its overseas interests or its allies, and to ensure the Afghan people can provide for their own security.
"We are being successful in those missions," Obama said.
The reason the United States can begin a drawdown of troops this year is "precisely because of the extraordinary work of our men and women in uniform," he said.
"What they've been able to do is to severely cripple al-Qaida's capacities. Obviously, bin Laden got the most attention, but even before the bin Laden operation, we had decimated the middle ranks and some of the upper ranks of al-Qaida," Obama said. "They're having a great deal of difficulty operating, a great deal of difficulty communicating and financing themselves. And we are going to keep the pressure on."
In addition, U.S. forces have been able to ramp up training of Afghan security personnel, he said.
Commenting about the recent violence in Afghanistan, Obama said he anticipates bombings "will probably go on for some time."
But, "the tide of war is receding," Obama said. "We have shifted to a transition phase."