In this April 30, 1975 file photo, a North Vietnamese tank rolls through the gates of the Presidential Palace in Saigon, signifying the fall of South Vietnam. The war ended on April 30, 1975, with the fall of Saigon, now known as Ho Chi Minh City, to communist troops from the north. (AP Photo/File)

In this April 29, 1975 file photo, mobs of Vietnamese people scale the wall of the U.S. Embassy in Saigon, Vietnam, trying to get to the helicopter pickup zone, just before the end of the Vietnam War. (AP Photo/Neal Ulevich, file)