ARLINGTON, Va. – Quoting letters of the fallen from the war in Iraq, President Bush vowed yesterday to a Memorial Day audience of military families and soldiers in uniform that the nation will honor its dead by striving for peace and democracy, no matter the cost.

“We must honor them by completing the mission for which they gave their lives: by defeating the terrorists,” the president told a supportive crowd of several thousand people at Arlington National Cemetery.

Mr. Bush’s remarks come as the American military supports a large weekend show of force in Baghdad by Iraqi forces aimed at halting attacks by insurgents. The violence has killed more than 700 people since Iraq’s new government was announced April 28. The sweep of Baghdad was answered by counterattacks by insurgents; and south of the city, two suicide bombers blew themselves up in a crowd of police officers, killing up to 30 people and wounding dozens.

The president’s tribute at Arlington came in sharply different circumstances from the Memorial Day visit Mr. Bush made to the cemetery’s Tomb of the Unknowns two years ago, just as the nation’s problems stemming from the Iraq war were becoming apparent.

Before his Memorial Day remarks in 2003, Bush had declared major combat operations at an end, the American government confidently predicted that weapons of mass destruction would be found, and American generals said troops were in the process of stabilizing Iraq. At that time, some 160 American soldiers had been killed in Iraq. Today, the total is more than 1,650.

Yesterday, Mr. Bush evoked the memories of American soldiers who have died, reading excerpts from the letters they wrote, in some cases letters that were to be opened only in the event that the soldier didn’t make it home.

“My death will mean nothing if you stop now,” National Guard Sergeant Michael Evans of Louisiana wrote in a letter home. Evans died January 28 while on patrol in western Baghdad, part of a major security operation to protect the first free Iraqi elections in more than 50 years.

“I know it’ll be hard, but I gave my life so you could live, not just live, but live free,” Evans wrote.

Mr. Bush’s nine-minute address was punctuated eight times by applause from a crowd of military families, some of whom were accompanied by soldiers in wheelchairs recovering from their wounds.

As he has done since American forces invaded Iraq in March 2003, the president said the war is part of a greater conflict necessitated by the September 11, 2001, terrorist attacks that claimed nearly 3,000 lives, toppled the World Trade Center, and heavily damaged the Pentagon, which is near the cemetery where Mr. Bush spoke.

“Two terrorist regimes are gone forever, freedom is on the march, and America is more secure,” Mr. Bush said of the end of the Taliban regime in Afghanistan and Saddam Hussein’s rule in Iraq.