MacArthur advised Congress that "there was no substitute for victory," and contradicted national policy. On April 11, 1951, President Truman fired MacArthur, replaced him with Matthew Ridgway, and in the process changed the nature of air warfare in Korea. The Air Force would still interdict the flow of supplies to Chinese units along the 38th Parallel and provide close air support to U.N. forces opposing them, but it would now also pressure the enemy into a settlement by inflicting maximum losses of men and materiel. The "police action" had become a war of attrition.
The Fifth Air Force's new commander, Lieutenant General Frank Everest, believed that interdiction was key to reducing the impact of Chinese offensives and U.N. ground losses. MiG-15s outnumbered F-86 Sabres over North Korea by five-to-one in 1951. Thus the Air Force's losses climbed as B-29s operated mainly at night. Complicating its air superiority campaign were air bases which the Chinese tried to build in North Korea to support their own forces and which FEAF was compelled to target. F-86s engaged MiGs in air-to-air combat and B-29s cratered the air bases' runways, forcing Communist jets to continue flying out of China and limiting their ability to challenge because of their short range. However, any bomb damage was quickly repaired by enemy labor units and necessitated continuous return missions. Interdiction, although costly, racked up long lists of destroyed trucks, trains, rail lines, and bridges, including the heavily-defended Yalu crossings. Nonetheless, supplies still reached Communist front lines in quantity by night. Medal of Honor recipient Captain John Walmsley, Jr., of the 8th Bombardment Squadron gave his life using his searchlight-equipped B-26 as a beacon to direct other B-26s while they bombed an enemy supply train on September 14, 1951. As it had in Operation STRANGLE in Italy during World War II, the Air Force learned that no air campaign was tougher than interdiction.
By the spring of 1952 the Chinese had won the battle of interdiction and the Americans had failed in their attrition strategy along the 38th Parallel. Communist representatives, first at Kaesŏng and then at Panmunjon, stalled peace talks and demanded mandatory repatriation for prisoners-of-war. General Weyland proposed to break the impasse by expanding the air war against North Korea. As U.N. casualties climbed and negotiations dragged on, the new American commander in Korea, General Mark Clark, accepted Weyland's proposal. In June 1952 he ordered the bombing of the Suiho Hydroelectric Complex, previously "off limits" and one of the largest facilities of its type in the world. It was a major exporter of electricity to Chinese industries across the border. A four-day onslaught over Suiho and other hydroelectric plants cost North Korea 90 percent of its power system. Through the remainder of 1952, the
