The U.S. must make every effort to be a nation worthy of your sacrifice, President Barack Obama said of the country's fallen troops on Memorial Day as he paid tribute to them in a speech at the Arlington National Cemetery in Virginia. 

While the war in Iraq has drawn to an end after nine years of fighting and the war in Afghanistan is winding down, Obama said, the pain still lingers for the families who lost loved ones in battle.

For the first [time] in nine years, Americans are not fighting or dying in Iraq, Obama said, as quoted by USA Today. We are winding down the war in Afghanistan, and our troops will continue to come home. After a decade under the dark cloud of war, we can see the light of a new day on the horizon.

Obama also noted that mourners can be seen every day at Arlington honoring and praying for troops who died defending the U.S.

These 600 acres are home to Americans from every part of the country who gave their lives in every part of the globe, the president said while speaking to a large audience -- including many veterans -- at the cemetery, the Associated Press reported.

At the cemetery, the president paid a special tribute to four Marines who were among first to die in Iraq. Maj. Jay Thomas Aubin, Capt. Ryan Anthony Beaupre, Staff Sgt. Kendall Damon Waters-Bey, and Cpl. Brian Matthew Kennedy were killed at the beginning of the Iraq War when their helicopter crashed near the Iraq-Kuwait border, reported USA Today.

Obama also honored Army Spec. David Hickman, who was the last American to die in Iraq. Hickman's vehicle was struck by a roadside bomb.

Today we come together as Americans to pray, to reflect and to remember these heroes, but tomorrow this hallowed place will once again belong to a smaller group of visitors who make their way through the gates and across these fields, in the heat and in the cold, in the rain and the snow, following a well-worn path to a certain spot and kneeling in front of a familiar headstone. You are the family and friends of the fallen, Obama said, according to CBS.

In his speech, Obama said he spoke with the Hickman family at Fort Bragg, N.C.

For the families here today, I will repeat what I said to the Hickmans: 'I cannot fully understand your loss. As a father, I cannot begin to imagine what it is like to receive that knock at the door and realize your worst fears have come true.' Obama said. But as commander-in-chief, I can tell you sending our troops into harm's way is the most wrenching decision I have to make. I can promise you that I will never do so, unless it is absolutely necessary, and that when we do, we must give our troops a clear mission and the full support of a grateful nation.

Defense Secretary Leon Panetta also spoke to the crowd at the cemetery. All the men and women who rest here are a constant reminder that freedom is not free, said Panetta, as reported by the AP.

Before speaking at Arlington, the president laid a wreath at the cemetery's Tomb of the Unknowns, in keeping with annual tradition.

Obama said that all men who die in combat share a special connection with one another. From the jungles of Vietnam to the mountains of Afghanistan, they stepped forward and answered the call, Obama said.

They fought for a home they may never return to, they fought for buddies they would never forget, he noted. While their stories may be separated by hundreds of years and thousands of miles, they rest here together side-by-side, row-by-row, because each of them love this country and everything it stands for more than life itself.