bombed, the two most famous were the Thanh Hoa bridge eight miles south of Hanoi and the Paul Doumer bridge in Hanoi itself. Both were critical to transport supplies flowing from China into North and South Vietnam. Hundreds of bombing sorties conducted over several years failed to bring down the solidly-built Thanh Hoa bridge. When the Johnson administration finally permitted the bombing of the Doumer bridge in 1967, fighter-bombers quickly dropped one span. After several weeks, repair crews put the bridge back into operation and it had to be bombed again. Over France in World War I, American airmen contested with Fokkers for air superiority and over Germany in World War II, with Focke-Wulfs and Messerschmitts. Over Korea they fought MiGs. Over North Vietnam they fought fewer MiGs as the struggle became primarily directed against surface-to-air missiles and antiaircraft artillery. When the Johnson administration approved the cessation of bombing north of the 19th parallel in the spring of 1968, North Vietnam agreed to negotiate. Peace negotiations began in Paris in November 1968, and the United States halted ROLLING THUNDER. The JCS then limited Air Force operations in North Vietnam to protective reaction missions. Aircraft would conduct reconnaissance and would strike only if attacked.
Meanwhile, in South Vietnam, the ground war worsened. In 1965 American commander, General William Westmoreland, oversaw the change of commitment in South Vietnam from a coastal enclave strategy for the protection of large cities, to direct ground involvement ("search and destroy" missions) into the interior after Communist forces in a massive campaign of close air support and interdiction. By 1968 over half a million American troops were engaged. Again, as it had in Korea, American strategy called for substituting air power for ground action whenever possible to reduce Army casualties. Ironically, while dropping less than one million tons of bombs on North Vietnam, the enemy, the United States dropped more than four million tons on South Vietnam, the ally. When Westmoreland ordered a major offensive into the "Iron Triangle" northwest of Saigon, more than 5,000 Air Force tactical strike sorties, 125 B-52 strikes, and 2,000 airlift sorties paved the way.
Operations included an extensive defoliation campaign (RANCH HAND) in which C-123 Providers and other transports sprayed 19 million gallons of herbicides over the jungles that provided convenient hiding places for Viet Cong guerrillas and North Vietnamese regular units out to ambush American ground troops. The overwhelming firepower brought by America to Vietnam gave Air Force airlift a major role in the war. Because jungle roads were rarely safe, Allied forces called on Army helicopters and Air Force C-47 Skytrains, C-119 Boxcars, C-123
