The United States Army Old Guard, officially known as the 3rd U.S. Infantry Regiment, is the oldest active-duty infantry unit in the U.S. Army, established in 1784. It is primarily responsible for ceremonial duties, including guarding the Tomb of the Unknown Soldier at Arlington National Cemetery and participating in state funerals and official ceremonies in Washington, D.C. In addition to its ceremonial role, the Old Guard also serves as a quick reaction force for the National Capital Region. The regiment is known for its precision and discipline, with soldiers undergoing rigorous training to maintain the highest standards of military conduct and appearance.