"This time of war began in Afghanistan, and this is where it will end," Obama said before a backdrop of armored military vehicles and a draped U.S. flag at the Bagram air base.
Obama's address to the nation capped a surprise visit that coincided with the anniversary of the death of Osama bin Laden, a mission that has become an unexpected focal point in his campaign for reelection.
The stated purpose for the trip was to sign a strategic partnership agreement with Afghanistan that Obama said would define "a new kind of partnership" between the nations, more than 10 1/2 years after the Sept. 11 attacks.
The agreement calls for the continuing reduction of the U.S. troop level while supporting the growth of "strong and sustainable" Afghan security forces. It also broadly outlines how Americans would continue to work with the Afghan government to fight terrorism and support development of the nation's infrastructure.
Answering critics of a timetable for withdrawal and those who would advocate a more immediate drawdown, the president said the U.S. goal was "not to build a country in America’s image, or to eradicate every vestige of the Taliban" but to "destroy Al Qaeda" while leaving enough time for the nation to stabilize.
"My fellow Americans, we have traveled through more than a decade under the dark cloud of war. Yet here, in the predawn darkness of Afghanistan, we can see the light of a new day on the horizon," the president said.
The administration and Obama's campaign have put a major emphasis on national security over the last week, questioning whether Mitt Romney would have ordered the same mission to take out Bin Laden. That's led to Republican charges that Obama is politicizing the military effort.
Obama, hours after speaking directly to the troops at Bagram, said that the nation was in the position to begin winding down its mission only because of the bravery of the nation's military.
"They met their responsibilities to one another, and the flag they serve under," Obama said. "In their faces, we see what is best in ourselves and our country."
As America's military commitments abroad wind down, Obama said, it is "time to renew America."
"An America where our children live free from fear, and have the skills to claim their dreams. A united America of grit and resilience, where sunlight glistens off soaring new towers in downtown Manhattan, and we build our future as one people, as one nation," he said.
Photo: Military personnel watch on a screen as President Obama delivers a live address at Bagram air base in Afghanistan. Credit: Charles Dharapak / Associated Press