BAGRAM AIR FIELD, Afghanistan - U.S. forces serving in Afghanistan and Iraq remembered friends and colleagues Monday in solemn Memorial Day ceremonies to commemorate all of their nation's war dead. As some soldiers paused, violence raged on in both places.

In Afghanistan, U.S.-led NATO forces launched air strikes against Taliban insurgents who had forced government forces to abandon a district in Nuristan, a remote province on the Pakistan border. NATO also said it killed one of the Taliban's top two commanders in the insurgent stronghold of Kandahar in a separate air strike.

At the Bagram Air Field, the largest U.S. military base in Afghanistan, about 400 soldiers in camouflage uniforms and brown combat boots stood at attention for a moment's silence as Gen. Stanley McChrystal, commander of some 94,000 U.S. troops in the country, led the ceremony. A bugler played Taps and a color guard displayed the U.S. flag and the flags of units serving in eastern Afghanistan, where the base is located about 30 miles north of Kabul.

A steel construction beam from the World Trade Center destroyed in the Sept. 11 attacks was unveiled, with the inscription "WTC 9 11 01." The beam was donated by the citizens' group the Sons and Daughters of America of Breezy Point, a suburb in Queens, N.Y., where 29 victims of the Sept. 11 attacks lived, according to a letter read aloud at the ceremony.

McChrystal praised the soldiers for their courage, given the likelihood that they will lose more friends during their tours. "The fact that people are willing to stand up and do what is difficult, they are willing to stand up and do what is frightening, and they are willing to stand up and do what often costs, really is the measure of not just a person but of a people," McChrystal said.

At Bagram, Maj. John Sherwood, 38, of San Antonio, said Memorial Day was more somber in Afghanistan than in the United States, as people remembered friends who died. "I think about a few people I knew, mostly back in Iraq," said Sherwood, of the 82d Airborne Division based in Fort Bragg, N.C.

In the Iraqi capital, hundreds of American troops gathered to remember their fallen comrades in one of ousted dictator Saddam Hussein's former palaces in Baghdad that is now part of the U.S. military's Camp Victory. Troops placed a wreath at the foot of a towering American flag in the palace, and a brass band played the American national anthem. Troops enjoyed cake after the ceremony.

Lt. Gen. Robert W. Cone, deputy commanding general for U.S. forces in Iraq, urged his countrymen to "take time today to think about those who made their freedom possible."

Separate attacks in Iraq killed four people, including a leader of anti-insurgent forces, and wounded several others, police and hospital officials said.