Before he left, General Hansell had introduced some reforms which were to have lasting effects. Engine failures were still a problem for the B-29 as late as mid-January of 1945, and the abort rate was running at 23 percent per mission. In order to reduce the abort rate, Hansell ordered a weight reduction program for the B-29 in which one of the fuel tanks was taken out and some of the 0.50-inch machine gun ammunition was removed, shaving over 6000 pounds from the weight of each plane. Maintenance was centralized under Hansell's headquarters rather than having it being split up between the various Bombardment Groups. As a result of these changes, B-29 endurance began to lengthen, engine life was extended from 200 to 750 hours, and the abort rate began to decline. By July of 1945, it was down to less then seven percent per operation.
In January of 1945, the 313th Bombardment Wing (6th, 9th, 504th, and 505th Bombardment Groups) under the command of Brig Gen John H. Davies took over the newly-built North Field on Tinian. They took part in a high-altitude daylight raid on Kobe on February 4.
This was the last of the raids on Japan for a while, General LeMay's B-29s being diverted to the campaign to capture Iwo Jima. Iwo Jima was considered vital to the B-29 campaign, since it could be used to base fighters capable of escorting the B-29s to Japan, as well as an emergency field midway between the Marianas and their targets.
Concerned about the relative failure of the B-29 offensive to deal any crippling blows to Japan, General LeMay issued a new directive on February 19. General LeMay had analyzed the structure of the Japanese economy, which depended heavily on cottage industries housed in cities close to major industrial areas. By destroying these feeder industries, the flow of vital components to the central plants could be slowed, disorganizing production of weapons vital to Japan. He decided to do this by using incendiary bombs rather than purely high-explosive bombs, which would, it was hoped, cause general conflagrations in large cities like Tokyo or Nagoya, spreading to some of the priority targets.
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