even more difficult than in Europe, resulting in a switch of tactics to low-level area bombing of cities with incendiaries. The wartime Chief of the USAAF, General of the Army Henry H. Arnold, contended that the conventional bombing had destroyed Japan's ability to wage war, and the atomic bombing of Hiroshima and Nagasaki had given the Emperor of Japan an excuse to end the war. The advent of nuclear weapons gave the strategic bombardment theorists encouragement that the factors that had limited the effectiveness of strategic bombing during the war could be overcome. Colonel Dale O. Smith wrote that: The bombing campaign called for in the war plans was both nuclear and conventional. By June 1948, components for about fifty Fat Man and two Little Boy bombs were on hand. These had to be assembled by specially trained Armed Forces Special Weapons Project assembly teams. Only Silverplate Boeing B-29 Superfortress bombers were capable of delivering nuclear weapons, and of the 65 that had been made, only 32 were operational at the start of 1948, all of which were assigned to the 509th Bombardment Group, which was based at Roswell Army Airfield in New Mexico. Trained crews were also in short supply; at the beginning of 1948 only six crews were qualified to fly atomic bombing missions, although enough personnel had been trained to assemble an additional fourteen in an emergency. But up to 20 percent of the target cities in the war plan were beyond the range of the B-29, requiring a one-way mission, which would expend the crew, bomb and aircraft. There were also doubts about the ability of the B-29 to penetrate Soviet air space; as a propeller-driven bomber, it was highly vulnerable to the new Soviet jet fighters, even at night. The B-29 was the mainstay of the bomber fleet in 1948, but that year the Convair B-36 Peacemaker was introduced into service. German victories in the early part of World War II had led to apprehension that the United Kingdom might be overrun. The Air Corps therefore invited design proposals for an intercontinental bomber that could reach Germany from bases in the United States. From this came the B-36. The aircraft pushed the state of the art at the time, but soon ran into development and schedule problems, and lost priority to the B-29. It was not canceled, and in 1943 when it looked like bases