 North Vietnamese tanks breached defenses on the outskirts of Saigon and the song "White Christmas" was broadcast, as the final signal for U.S. withdrawal.Master Sergeant Juan J. Valdez was the noncommissioned officer in charge of the Marine security guard detachment stationed at the US Embassy, Saigon.He had previously served from 1965 to 1967 with Company B, 3d Amphibian Tractor Battalion, attached to 2d Bn, Fourth Marine Regiment and was now on his second tour.