"Each of you have stepped forward to defend your country," Bush told the 1,012 members of the U.S Air Force Academy class of 2008. "I thank you for making this courageous choice."

After recalling battles, equipment and challenges of World War II, Bush said, the nation now faces "evil men who despise freedom and despise America."

Improved technologies advance the military's capabilities, so modern warfare can be waged more precisely against the nation's enemies, he said.

"We can work toward this noble goal: Defeating the enemies of freedom by sparing innocent people," he said.

Fighting a more precise war means "we can make war less likely," Bush said. "It is a powerful deterrent that America is willing and able to target regimes directly."

Before getting into the heart of his speech, Bush exercised a bit of executive privilege.

"I hereby absolve all cadets from restrictions for minor conduct offenses," Bush told the cheering crowd at the Colorado Springs, Colo., military academy.

As for grades, he said, "some things are beyond the powers of the president."