Page:A Concise History of the U.S. Air Force.djvu/52

 ing at Inchon on September 15, coupled with a U.N. drive north from the Pusan Perimeter, clearing South Korea of North Korean forces. In early October the U.N. changed its objective from saving South Korea to unifying all of Korea under a pro-Western government. Before the end of the month, as MacArthur's army approached the Yalu River separating China from North Korea, signs pointed to probable Communist Chinese intervention. The Air Force switched to interdicting the flow of men and materiel across the Yalu bridges. The freezing of the Yalu River in January 1951, and rules of engagement that forbade American overflights of Chinese territory on the north end of the bridges, condemned the effort to failure. B-29s had to fly above 20,000 feet to escape antiaircraft artillery fire from the Chinese side of the Yalu, but they could not fire back. That altitude and bombs errantly falling on Chinese territory insured little success. Bombing became even more difficult when China escalated the conflict in November 1950 by sending Soviet-provided MiG-15 jet fighters, launched from safe sanctuary on lightning attacks against American aircraft, especially FEAF B-29s. The airspace just south of the Yalu River in northwestern Korea became known as "MiG Alley." The performance advantages of the MiG-15 in speed and altitude initially held sway over propeller-driven P-51 Mustangs (pursuit aircraft redesignated by the Air Force as fighters in June 1948), jet-powered F-80 Shooting Stars, and even newer F-84 Thunderjets. Chinese Communist forces counterattacked on November 26, driving U.N. units back toward South Korea. For the U.S. Air Force, this meant a renewed concentration on interdiction, combined with a campaign to maintain air superiority against the MiG-15s. Air Force airlift brought 1,600 tons of supplies to Marines cut off at Changjin (more widely known by its Japanese name, Chosin) Reservoir and evacuated 5,000 wounded. After retreating, U.N. forces stabilized along the 38th parallel in early 1951 and the war deteriorated into a series of small, bloody battles, with no significant movement by either side. War objectives changed again. Peace talks opened in July 1951. They were backed by a new American strategy to force high rates of attrition on the enemy. It would be up to FEAF, now under Lieutenant General Otto Weyland, and U.S. naval aviation to carry the war beyond the front, to pressure North Korea and China into a ceasefire, substituting air power whenever possible for ground operations that inevitably resulted in high casualties. This strategy presented new threats and complications for the Air Force. Doctrine dictated strikes against the enemy's industrial fabric, but the bombing operations of 1950 had destroyed these limited North Korean targets. Industries supporting the Communist war effort, located in