'Black Jack' the riderless horse followed the caisson carrying the President's casket. A riderless horse symbolizes fallen soldiers. Traditionally, simple black riding boots are reversed in the stirrups to represent a fallen leader looking back on his troops for the last time. Black Jack was the last of the military horses branded with the Army's U.S. brand and his Army serial number 2V56. He died on February 6, 1976, and was buried with full military honors.