Vietnam S U.S. Toops

Armored Personnel Carriers with troops of the 11th Armored Cavalry Regiment aboard grind their way through underbrush in Tay Ninh Province, about a mile and a half away from the Cambodian border on March 18, 1970, as they proceed towards an enemy base camp. The troops were checking the area to determine effectiveness of a recent B-52 bomber strike on the base camp. (AP Photo/Charles Ryan)

M113 armored cavalry assault vehicles, or ACAVs, and M551 Sheridan light tanks of the 11th Armored Cavalry Regiment plow through rough terrain about a mile and a half from the Cambodian border on March 18, 1970. (AP Photo/Charles Ryan)

AP Photo/Charles Ryan