WASHINGTON -- At the onset of the Memorial Day weekend, President Bush used his weekly radio address to pay tribute to American veterans, past and present. They have "given their lives for our nation," Bush said. "Our citizens live in freedom because patriots are willing to serve and sacrifice for our liberty."Memorial Day is in remembrance of the nation's war dead. Bush noted, "This year marks the 60th anniversary of the end of World War II." Some 400,000 Americans, he observed, died in that conflict.Today, the nation is again at war -- in Iraq, Afghanistan, and elsewhere. "A new generation of Americans is making its own sacrifice on behalf of peace and freedom, and some have given their lives," Bush said.To honor the nation's war dead, the president said he will lay a wreath at Arlington National Cemetery on May 30, Memorial Day."We mourn their loss, and we honor their sacrifice," Bush said. "We pray for their families. And we take heart in knowing that these men and women believed deeply in what they were fighting for."The president noted that he gave the commencement address at the U.S. Naval Academy May 27."These new officers will soon be serving on ships, flying combat missions, and leading our troops into battle against dangerous enemies," Bush said. But, he added, "they are prepared for the challenges ahead -- morally, mentally, and physically. The American people can be confident that their freedom is in good hands."The president cited the example set by two recently slain veterans: Sgt. Rafael Peralta, a Mexican immigrant who enlisted in the Marine Corps the day after receiving his "green card," which allows immigrants to legally work in the United States; and Sgt. Christopher Swisher, a native of Lincoln, Nebraska, who joined the Army a year after graduating from high school.Before the battle of Fallujah, Iraq, Peralta wrote to his 14-year-old brother. "We are going to defeat the insurgents. Be proud of me. I'm going to make history and do something that I always wanted to do."A few days later, Bush said, "Sgt. Peralta gave his life to save his fellow Marines."Bush said Swisher was "killed in an ambush while on patrol in Baghdad." Before dying, Swisher told his loved ones: "If anything happens to me, I'm doing what I what I want to be doing: I'm protecting my family and my home."In their hometowns, Bush said, "these Soldiers, Sailors, Airmen, and Marines are more than names on a roll of honor. They were friends and neighbors, teachers and coaches, classmates and colleagues. Each was the most important person in someone's life. Each had hopes for the future, and each left a place that can never be filled."Today, as in many times throughout its history, America is at war "not to conquer but to liberate," Bush said. "We go to war reluctantly because we understand the high cost of war."The U.S. military, he added, is "training Iraqi and Afghan forces so they can take the fight to the enemy and defend their own countries." When that happens, Bush said, "our troops will return home with the honor they have earned. ... (They) have the respect and gratitude of our entire nation."