In April 1970, Sâr flew to Hanoi. He stressed to Lê Duẩn that while he wanted the Vietnamese to supply the Khmer Rouge with weapons, he did not want troops: the Cambodians needed to oust Lon Nol themselves. North Vietnamese armies, in collaboration with the Viet Cong, nevertheless invaded Cambodia to attack Lon Nol's forces; in turn, South Vietnam and the United States sent troops to the country to bolster his government. This pulled Cambodia into the Second Indochina War already raging across Vietnam. The U.S. dropped three times as many bombs on Cambodia during the conflict as they had on Japan during World War II. Although targeting Viet Cong and Khmer Rouge encampments, the bombing primarily affected civilians. This helped fuel recruitment to the Khmer Rouge, which had an estimated 12,000 regular soldiers at the end of 1970 and four times that number by 1972.