The Sentinels at the Tomb of the Unknown Soldier stand guard 24 hours a day year-round to protect those that gave everything in service of their nation. What does it take to become a Sentinel? In our new series "Behind the Old Guard," we take an in-depth look at some of the specialty units in the 3d U.S. Infantry Regiment.
(Video by Staff Sergeant Chris Ballentine)
(Historic and aerial photos courtesy of U.S. Library of Congress http://www.loc.gov/)