1972 in the Vietnam War the number of air raids against North Vietnam during all of 1971. Prime Minister Lon Nol declared President of Cambodia. Unlike the former Cambodian leader, Norodom Sihanouk, Lon Nol was a U.S. ally. The U.S. 101st Airborne Division left South Vietnam, the last U.S. ground combat division to be withdrawn from South Vietnam. The Khmer Rouge bombarded with artillery Phnom Penh, the capital city of Cambodia, killing more than 100 civilians. This was the heaviest attack on Phnom Penh since the Cambodian Civil War began in 1970. The United States boycotted peace negotiations in Paris with the North Vietnamese, citing
1965 in the Vietnam War order and evaded pursuit by the ARVN. President Johnson halted the bombing of North Vietnam under Operation Rolling Thunder in an attempt to induce the North Vietnamese to negotiate a peace agreement. North Vietnam instead said the bombing halt was only "an effort to camouflage American intensification of the war." North Vietnam's leader Ho Chi Minh met with Chinese leader Mao Zedong in China. Ho said that North Vietnam would "take the main burden of the war by themselves" but requested additional Chinese economic and military support. Mao agreed and they set the ground rules for Chinese assistance: North Vietnamese