 Complete the following phrase:  From 1965 to 1973, U.S. troops fought at the request of the governments of South Vietnam, Laos, and Cambodia during the Vietnam War against the military of North Vietnam and against Viet Cong, Pathet Lao, and Khmer Rouge insurgents. President Lyndon Johnson escalated U.S. involvement following the Gulf of Tonkin Resolution. North Vietnam invaded Laos in 1959, and used 30,000 men to build invasion routes through Laos and Cambodia. North Vietnam sent 10,000 troops to attack the south in 1964, and this figure increased to 100,000 in 1965. By early 1965, 7,559 South Vietnamese hamlets had been destroyed by the Viet Cong. The CIA organized Hmong tribes to fight against the Pathet Lao, and used Air America to drop 46 million pounds of foodstuffs...transport tens of thousands of troops, conduct a highly successful photoreconnaissance program, and engage in numerous clandestine missions using night-vision glasses and state-of-the-art electronic equipment. After sponsoring a 