The flammability of Japan's large cities, and the concentration of munitions production there, made strategic bombing the preferred strategy of the Americans. The first efforts were made from bases in China. Massive efforts (costing $4.5 billion) to establish B-29 bases there had failed when in 1944 the Japanese Army simply moved overland and captured them. The Marianas (especially the islands of Saipan and Tinian), captured in June 1944, gave a close, secure base for the very-long-range B-29. The "Superfortress" (the B-29) represented the highest achievement of traditional (pre-jet) aeronautics. Its four 2,200 horsepower Wright R-3350 supercharged engines could lift four tons of bombs 3,500 miles at 33,000 feet (high above Japanese flak or fighters). Computerized fire-control mechanisms made its 13 guns exceptionally lethal against fighters. However, the systematic raids that began in June 1944, were unsatisfactory, because the AAF had learned too much in Europe; it overemphasised self-defence. Arnold, in personal charge of the campaign (bypassing the theatre commanders) brought in a new leader, General Curtis LeMay. In early 1945, LeMay ordered a radical change in tactics: remove the machine guns and gunners, fly in low at night. (Much fuel was used to get to 30,000 feet; it could now be replaced with more bombs.) The Japanese radar, fighter, and anti-aircraft systems were so ineffective that they could not hit the bombers. Fires raged through the cities, and millions of civilians fled to the mountains.
