The second full-scale strike did not occur until July 7, 1944. By then, Arnold, impatient with Wolfe's progress, had replaced him temporarily with Brigadier General LaVern G. Saunders, until Major General Curtis E. LeMay could arrive from Europe to assume permanent command. Unfortunately, the three-week delay between the first and second missions reflected serious problems that prevented a sustained strategic bombing campaign from China against Japan. Each B–29 mission consumed tremendous quantities of fuel and bombs, which had to be shuttled from India to the China bases over the Himalayas, the world's highest mountain range. For every Superfortress combat mission, the command flew an average of six B–29 round-trip cargo missions over the Hump, using both tactical aircraft and B-29s modified as fuel tankers. When it was immediately apparent that the operation would never be self-sustaining, the Air Transport Command was called upon to support Matterhorn with allocations on its Hump airlift, taken from the allocations to the Fourteenth Air Force already in China. In September 1944 70 C-109s were added to the effort, flown by surplus B-29 crews, but XX Bomber Command, fearful of diversions to other agencies, resisted all attempts to have them operated by ATC. Its transport procedures contradicted those of ATC, however, limiting its efficiency, and beginning in November 1944 its B-29s were withdrawn from the airlift and the C-109s transferred to ATC. With plans already developed to shut down B-29 forward basing in China at the end of January 1945, ATC took over the logistical supply of the bases in China, too late to provide the volume required to stockpile materiel. In the end, 42,000 tons of cargo were delivered over the Hump to XX Bomber Command between April 1944 and January 1945, nearly two-thirds of it by ATC.