Fighting intensifies as Cambodian government forces battle with Khmer Rouge, Viet Cong, and North Vietnamese forces northeast of Phnom Penh. In March 1970, a coup led by Cambodian General Lon Nol had overthrown the government of Prince Norodom Sihanouk in Phnom Penh. Lon Nol and his army, the Forces Armees Nationale Khmer (FANK), with U.S. support and military aid, fought the Communist Khmer Rouge for control of Cambodia. In addition, the government forces had to contend with the North Vietnamese and Viet Cong, who continued to use Cambodia as a sanctuary for their forces attacking into South Vietnam. In this round of the fighting, the major engagements occurred around the provincial capitals of Kompong Thom and Rumlong. The Communists began a siege of these garrisons after their demolition frogmen destroyed a crucial bridge along Route 6, the main supply line for the 20,000 Cambodians on the northeast front. Some 400 government soldiers were reported dead as a result of the combat.