3d U.S. Infantry Regiment (The Old Guard) | 2,943 followers on LinkedIn. Army's Official Ceremonial Unit / Escort to the President / Security for Washington, D.C. in time of emergencies | The 3d U.S. Infantry Regiment, traditionally known as "The Old Guard," is the oldest active-duty infantry unit in the Army, serving our nation since 1784. The Old Guard is the Army's official ceremonial unit and escort to the president, and it also provides security for Washington, D.C., in times of national emergency or civil disturbance.