Each year for the past 40 years, the 3rd U.S. Infantry (The Old Guard) has honored America's fallen heroes by placing American flags before the gravestones and niches of service members buried at both Arlington National Cemetery and the U.S. Soldier's and Airmen's Home National Cemetery just prior to Memorial Day weekend.

This tradition, known as "flags in," has been conducted annually since The Old Guard was designated as the Army's official ceremonial unit in 1948. Every available soldier in the 3rd U.S. Infantry participates, placing small American flags one foot in front and centered before each grave marker.

During an approximately three-hour period, the soldiers place flags in front of more than 260,000 gravestones and about 7,300 niches at the cemetery's columbarium. Another 13,500 flags are placed at the Soldier's and Airmen's Cemetery. As part of this yearly memorial activity, Old Guard soldiers remain in the cemetery throughout the weekend, ensuring that a flag remains at each gravestone.

American flags are also placed at the graves of each of the four unknown service men interred at the Tomb of the Unknowns, by the Tomb Sentinels. All flags are removed after Memorial Day before each cemetery is opened to the public.