President Barack Obama attended Memorial Day services at Arlington National Cemetery on Sunday where he gave a speech and layed a wreath at the Tomb of the Unknowns. (Sandi Moynihan/The Washington Post)

Honoring the nation’s fallen amid the longest war in U.S. history, President Obama laid a wreath near the Tomb of the Unknowns on Monday and spoke of troops in Afghanistan, asking that the country “not forget our nation is still at war.”

Obama recalled several recent deaths in the Afghan conflict and a mother’s recent plea that those serving not fade from the public mind.

“We must remember our countrymen are still serving, still fighting, still putting their lives on the lines for us,” he said, speaking beneath a marble arch in the amphitheater at Arlington National Cemetery.

For Obama, the occasion marked the first Memorial Day of his second term. It was a sunny May morning that warmed as noon approached, without the sweltering heat that has attended some years.

Thousands of people walked the cemetery’s solemn grounds, many bearing roses and small American flags. Some waited to see the president’s tribute, and others sought out quiet remembrances at grave sites.

Many spoke of the importance of not forgetting.

After Obama’s remarks, he was expected to stop at Section 60, where many service members from the wars in Iraq and Afghanistan are buried.

Patrick Minihan, 40, a teacher from Massachusetts who deployed to Afghanistan and Iraq during service in the Army, was spending his 11th Memorial Day at the cemetery.

He listened to Obama’s remarks and intended to go to Section 60 with a friend afterward.

“For me, it’s important to see the faces there to recognize these are not just numbers, but there is a specific human cost,” he said.