ARLINGTON, Va. (AP) -- President Barack Obama said Monday that Americans must honor the sacrifices of their fighting men and women, particularly at a time when the U.S. combat role in Iraq has ended and the country's involvement in Afghanistan is winding down.

Speaking at Memorial Day ceremonies at Arlington National Cemetery, Obama said he worries that the country's servicemen and women aren't being fully appreciated in an era in which "most Americans are not directly touched by war." He said he couldn't explain that phenomenon but said it might have something to do with the all-volunteer military force and advanced technology that now permits the United States to accomplish some military missions with far fewer personnel.

But Obama did say that even as "we turn a page" away from Iraq, and Afghanistan by the end of 2014, "let us never forget that the nation is still at war."

He said that some troops and military families "mention to me their concern about whether the country fully appreciates" them.

Obama's Memorial Day appearance at the venerable Arlington burial grounds came four days after he declared in a major national security address that the U.S. has taken down the al-Qaida terrorist organization, particularly in the aftermath of the killing of leader Osama bin Laden, although terrorist threats remain and the country cannot afford to let its vigilance slide.

Obama spoke on a sun-splashed morning at the amphitheater of Arlington National Cemetery after he placed a wreath at the Tomb of the Unknowns. That was preceded by a playingof the National Anthem and followed by the placing of "Taps."

In his speech, he said that Arlington "has always been home to men and women who are willing to give their all ... to preserve and protect the land that we love."

He praised the selflessness that "beats in the hearts" of America's uniformed military troops.

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  • Memorial Day Commemorated At Arlington National Cemetery

    ARLINGTON, VA - MAY 27: U.S. President Barack Obama and Major Gen. Michael S. Linnington stand before a wreath ceremony on Memorial Day at the Tomb of the Unknowns at Arlington National Cemetery on May 27, 2013 in Arlington, Virginia. For Memorial Day President Obama is paying tribute to military veterans past and present who have served and sacrificed their lives for their country. (Photo by Mark Wilson/Getty Images)

  • Memorial Day Commemorated At Arlington National Cemetery

    ARLINGTON, VA - MAY 27: U.S. President Barack Obama positions a commemorative wreath during a ceremony on Memorial Day at the Tomb of the Unknowns at Arlington National Cemetery on May 27, 2013 in Arlington, Virginia. For Memorial Day President Obama is paying tribute to military veterans past and present who have served and sacrificed their lives for their country. (Photo by Mark Wilson/Getty Images)

  • Memorial Day Commemorated At Arlington National Cemetery

    ARLINGTON, VA - MAY 27: U.S. President Barack Obama positions a commemorative wreath during a ceremony on Memorial Day at the Tomb of the Unknowns at Arlington National Cemetery on May 27, 2013 in Arlington, Virginia. For Memorial Day President Obama is paying tribute to military veterans past and present who have served and sacrificed their lives for their country. (Photo by Mark Wilson/Getty Images)

  • Memorial Day 2013

    Members of the Third US Infantry Regiment, The Old Guard, place flags in front of graves in Section 60 of Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    A US military veteran stencils the name of a fallen comrade at the Vietnam Memorial in Washington on May 25, 2013 as the country marks Memorial Day on May 27. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    Women in traditional Vietnamese garb fly the flag of the former South Vietnam as members of the US military veterans' Rolling Thunder bikers group parade in Washington on May 26, 2013 as the country marks Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    A man salutes as members of the US military veterans' Rolling Thunder bikers group ride past in Washington on May 26, 2013 as the country marks Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    Members of the US military veterans' Rolling Thunder bikers group parade in Washington on May 26, 2013 as the country marks Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    Two women hold up signs thanking the troops as members of the US military veterans' Rolling Thunder bikers group ride past in Washington on May 26, 2013 as the country marks Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    A woman looks at the grave of a soldier who fell during World War II, during services to mark US Memorial Day at the Manila American Cemetery in Fort Bonifacio in Manila on May 26, 2013. At least 17,000 graves are in the park that pays tribute to US and Philippines soldiers that fought side-by-side during World War II. The US marks Memorial Day on May 27. AFP PHOTO / NOEL CELIS (Photo credit should read NOEL CELIS/AFP/Getty Images)

  • Memorial Day 2013

    A woman walks amongst the graves of soldiers who fell during World War II, searching for a grave of a relative during a service to mark US Memorial Day at the Manila American Cemetery in Fort Bonifacio in Manila on May 26, 2013. At least 17,000 graves are in the park that pays tribute to US and Philippines soldiers that fought side-by-side during World War II. The US marks Memorial Day on May 27. AFP PHOTO / NOEL CELIS (Photo credit should read NOEL CELIS/AFP/Getty Images)

  • Memorial Day 2013

    US war veteran Ken Fuller (C-in wheelchair) is helped by relatives as he visits the halls displaying engraved names of soldiers who fell during World War II, at services to mark US Memorial Day at the Manila American Cemetery in Fort Bonifacio in the Philippine capital Manila on May 26, 2013. At least 17,000 graves are in the park that pays tribute to US and Philippines soldiers that fought side-by-side during World War II. The US marks Memorial Day on May 27. AFP PHOTO / NOEL CELIS (Photo credit should read NOEL CELIS/AFP/Getty Images)

  • Memorial Day 2013

    US military veterans gather to pay their respects to fallen comrades at the Vietnam Memorial in Washington on May 25, 2013 as the country marks Memorial Day on May 27. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    People gather to pay their respects at the Vietnam Memorial in Washington on May 25, 2013 as the country marks Memorial Day on May 27. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    A Vietnam war veteran points to a name on the Vietnam Memorial wall in Washington on May 24, 2013 as the country prepares to celebrate Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    People gather at the Vietnam Memorial in Washington on May 24, 2013 as the country prepares to celebrate Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    A US war veteran pays his respects at the Vietnam Memorial in Washington on May 24, 2013 as the country prepares to celebrate Memorial Day. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

  • Memorial Day 2013

    Staff Sergeant Karrin Kampa (L) of the Third US Infantry Regiment, The Old Guard, place flags in front of graves at Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    Members of the Third US Infantry Regiment, The Old Guard, place flags in front of graves at Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    A member of the Third US Infantry Regiment, The Old Guard, places flags in front of graves at Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    Staff Sergeant Joelle Monroe (R) of the Third US Infantry Regiment, The Old Guard, place flags in front of a grave at Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    Staff Sergeant Joelle Monroe (L) of the Third US Infantry Regiment, The Old Guard, placees flags in front of a graves at Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    A member of the Third US Infantry Regiment, The Old Guard, salutes after placing a flag infront of a grave in Section 60 of Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    A member of the Third US Infantry Regiment, The Old Guard, places a flag infront of a grave in Section 60 of Arlington National Cemetery on May 23, 2013 in Arlington, Virginia ahead of Memorial Day. Memorial Day is in honor of those who died while serving in the armed forces of the US. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Memorial Day 2013

    President Barack Obama speaks at the Memorial Amphitheater at Arlington National Cemetery during Memorial Day Observance, Sunday, May 27, 2013, in Arlington, Va, (AP Photo/Cliff Owen)

  • Memorial Day 2013

    First lady Michelle Obama, right, waves as she arrives to take her seat for the Memorial Day Observance at the Memorial Amphitheater at Arlington National Cemetery, May 27, 2013, in Arlington, Va. (AP Photo/Pablo Martinez Monsivais)

  • Memorial Day 2013

    President Barack Obama speaks at the Memorial Amphitheater at Arlington National Cemetery during Memorial Day Observance, Sunday, May 27, 2013, in Arlington, Va, (AP Photo/Pablo Martinez Monsivais)

  • Memorial Day 2013

    A young spectator shields her eyes from the sun with an American flag during a Memorial Day wreath laying at the Franklin D. Roosevelt Four Freedoms Park on Roosevelt Island, Monday, May 27, 2013, in New York. (AP Photo/John Minchillo)

  • Memorial Day 2013

    Seamen from the Navy Operational Support Center of New York City march through a crowd of spectators after a Memorial Day wreath laying at the Franklin D. Roosevelt Four Freedoms Park on Roosevelt Island, Monday, May 27, 2013, in New York. (AP Photo/John Minchillo)

  • Memorial Day 2013

    Seaman Daniel Odoi of the Navy Operational Support Center of New York City presents the American flag during a Memorial Day wreath laying at the Franklin D. Roosevelt Four Freedoms Park on Roosevelt Island, Monday, May 27, 2013, in New York. (AP Photo/John Minchillo)

  • Memorial Day 2013

    Navy Petty Officer Mark Jones of the Navy Operational Support Center of New York City rolls the American flag after a Memorial Day wreath laying at the Franklin D. Roosevelt Four Freedoms Park on Roosevelt Island, Monday, May 27, 2013, in New York. (AP Photo/John Minchillo)

  • Memorial Day 2013

    Arlington National Cemetery is ready for President Barack Obama's Memorial Day address in Arlington, Va., Monday, May 27, 2013. (AP Photo/Cliff Owen)

  • Memorial Day 2013

    Marine Staff Sgt. Travis Hassell, center, and his son Issac show off Francis Slate's, left, Honorable Discharge Card from the U.S. Army Dec. 3, 1945, as they wait for President Barack Obama to deliver his Memorial Day address at Arlington National Cemetery in Arlington, Va., Monday, May 27, 2013. (AP Photo/Cliff Owen)

  • Memorial Day 2013

    An Army officer walks up the steps of the Ampitheater where President Barack Obama will delivers his Memorial Day address at Arlington National Cemetery in Arlington, Va., Monday, May 27, 2013. (AP Photo/Cliff Owen)

  • Memorial Day 2013

    A US Marine walks alongside a woman through Section 60, the area of the cemetery primarily for members of the military killed in the wars in Iraq and Afghanistan, during Memorial Day at Arlington National Cemetery in Arlington, Virginia, May 27, 2013. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)

  • Memorial Day 2013

    A woman carries flowers past grave markers in Section 60, the area of the cemetery primarily for members of the military killed in the wars in Iraq and Afghanistan, during Memorial Day at Arlington National Cemetery in Arlington, Virginia, May 27, 2013. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)

  • Memorial Day 2013

    In this photo provided by the Florida Keys News Bureau a Florida Keys manatee mailbox in Islamorada, Fla., is decorated in red, white and blue Sunday, May 26, 2013, to honor Memorial Day. (AP Photo/Florida Keys News Bureau, Andy Newman)

  • Memorial Day 2013

    A boy rides his bike past crosses that bear the names of College Point veterans during the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Faith Roesch, 6, participates in the the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Joe Schulmann pauses in prayer over a cross bearing the name of his neighbor, Michael Wick, who was killed during the Vietnam War, at the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Carol Brandt, 3, right, talks with her father Matthew Brandt arms during the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    A fife and drum band participates in the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Sisters Lucia, 6, right, and Adriana, 2, DiPiano watch as a fife and drum band pass by during the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    A float passes by during the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Lilly Shirin, 8, takes pictures during the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Bob Lewis looks over a field of crosses with names while participating in the College Point Memorial Day Parade in New York, Sunday, May 26, 2013. Lewis made the crosses, 137, for all the service members from College Point that were killed from the Civil War to the Vietnam War. (AP Photo/Seth Wenig)

  • Memorial Day 2013

    Rows of U.S. flags frame the moon above the Brig. Gen. William C. Doyle Veterans Memorial Cemetery, in Wrightstown, N.J., Sunday, May 26, 2013. On Friday, Boy Scouts placed thousands of flags on veterans' graves for Memorial Day. (AP Photo/Mel Evans)

  • Memorial Day 2013

    A veteran takes photographs of the wall of the the Vietnam Veterans Memorial, ahead of Memorial Day in Washington, Sunday, May 26, 2013. (AP Photo/Molly Riley)

  • Memorial Day 2013

    A rose is placed at the wall of the the Vietnam Veterans Memorial, ahead of Memorial Day in Washington, Sunday, May 26, 2013. (AP Photo/Molly Riley)

  • Vietnam Veterans Memorial

    A veteran looks at the names of those who died etched into the wall of the Vietnam Veterans Memorial, ahead of Memorial Day in Washington, Sunday, May 26, 2013. (AP Photo/Molly Riley)

  • Memorial Day 2013

    Two-year-old Benjamin Pontes helps his mom Cindy place flags on veterans' graves at Riverside National Cemetery in Riverside, Calif., on Saturday, May 25, 2013. They were with Anaheim Police Officer Brennan Leininger's group of several volunteers. (AP Photo/The Orange County Register, Mindy Schauer) MAGS OUT; LOS ANGELES TIMES OUT.