ARLINGTON, Va. — On a cold, rain-soaked Veterans Day, President Barack Obama walked slowly through the white, stone markers at the section of Arlington National Cemetery reserved for troops killed in Iraq and Afghanistan, the two wars he oversees as commander in chief.

Obama led the nation Wednesday in observing Veterans Day with a traditional wreath-laying ceremony at the Tomb of the Unknowns at Arlington before an unannounced visit to the section reserved for those who fought in Iraq and Afghanistan.

"We gather here mindful that the generation serving today already deserves a place alongside previous generations for the courage they have shown and the sacrifices that they have made," Obama said in a brief speech following the wreath-laying. Obama pledged he would do right by all veterans and families, saying: "America will not let you down."

The president spoke one day after honoring the victims of a shooting rampage at Fort Hood, Texas. He said he was struck by the determination of the soldiers there, a quality that unites generations of American servicemen.

"To all of them — to our veterans, to the fallen and to their families — there is no tribute, no commemoration, no praise that can truly match the magnitude of your service and your sacrifice," he said.

The nation observed Veterans Day from remembrances at the nation's capital to a New York City parade to ceremonies in towns and cities across the nation and overseas.

At Camp Eggers in Kabul, soldiers observed a moment of silence for the more than 800 U.S. service members who have died in Afghanistan, Pakistan and Uzbekistan since the 2001 invasion to oust the Taliban regime.

The Navajo Code Talkers were special guests at the New York parade's opening ceremony, where a wreath was laid at the World War I Eternal Light Monument in Madison Square Park. As young Marines during World War II, the Code Talkers used secret Navajo language-encrypted military terms that the Japanese were never able to crack.

As the Code Talkers were introduced, the crowd — which included World War II veteran and actor Tony Curtis — let out a loud cheer.

An American Red Cross event in Washington kicked off the start of a program called Holiday Mail for Heroes, which lets the public send holiday greeting cards that aren't addressed to a particular service member. Under a Defense Department policy, ordinary mail addressed to "any soldier" has to be returned to the sender. The cards will be screened, sorted and distributed to military hospitals and bases nationally and overseas as well as to veterans and military family members.