Soldiers were first placed at the Tomb of the Unknown Soldier in 1926. Their primary responsibility was to prevent people from climbing or stepping on the Tomb. Beginning in 1937, guards were stationed there 24 hours a day. Since 1948, soldiers from the 3rd U.S. Infantry Regiment, called “The Old Guard,” have protected the Tomb. The soldiers are replaced in an elaborate changing-of-the-guard ceremony that occurs every hour or half hour, depending on the day.