Thursday, September 10, 2015

Operation Matterhorn

 The Captain Nicolas VanWingerden Crew, B-29, China/Burma/India.

From June of 1944 through January of 1945, four groups (sixteen squadrons) of B-29 bombers were deployed through airfields built by tens of thousands of Chinese laborers in the area of Chengdu – at Guanghan, Qionglai, Pengshan, and Xinjin.   They comprised the 58th Bombardment Wing of the new Twentieth Air Force.  This was the strategic bombing air force which implemented the dream of the air power pioneers such as General Arnold. 

The strategic plan for “Operation Matterhorn,” approved at the Quebec and Cairo Conferences, was:  gather a force of the new long-range Boeing B-29s in India, advance loaded bombers to the bases near Chengdu where they would refuel, and launch long distance raids against Japan.  Histories of the operation emphasize President Roosevelt’s personal commitment to opening a bombing campaign from China against Japan.  The Twentieth Air Force was not placed under any of the CBI theatre commanders (Arnold knew Stilwell and Chennault would try to use the B-29s to support their own operations), but was rather was an autonomous command under the Joint Chiefs of Staff.

The supply problems were daunting.  Ships with materiel, fuel, and personnel traveled from the U.S. via lengthy and roundabout Atlantic or Pacific routes to Karachi or Calcutta.  Before any raid from India to China to Japan could be mounted, fuel had to be transported to the airfields near Chengdu.  B-29s, intended for bombing, flew preparatory missions that carried only fuel (seven tons per mission) over the Hump to China.  It took six missions over the Hump to provide enough fuel for one mission to Japan.  There were losses of aircraft and men on these supply missions, which also reduced the active service life of the engines and airframes.

The first raid against Japan -- a 3200-mile mission -- was conducted the night of June 14-15, 1944.  The numbers testify to the difficulty of the task.  Ninety two aircraft left India, but only 79 reached China.  Seventy-five aircraft took off, but only 68 reached the Chinese coast and only 47 attacked the target, the Yawata Iron Works.  Fifteen aircraft bombed visually and 32 bombed by radar.  Only one bomb hit the target.  It was a harbinger of difficulties to come.

The XX Bomber Command continued to press its attacks, including some missions against Japanese targets in Manchuria, Taiwan, and China.  Its effectiveness increased with the assignment of Major General Curtis LeMay to the CBI and as it adopted new procedures -- a different formation, lead crews to find and mark targets, control of the bomb run by both bombardier and radar operator, and different mixes of high-explosive and incendiary bombs.  But so did the effectiveness of the Japanese defenses.

By the end of 1944 the Command had lost 147 bombers.  It was evident that the attacks against Japan mounted from Chengdu were too expensive in men, aircraft, and material to continue.  The last attack from Chengdu -- against Japanese targets in Taiwan -- was conducted on January 15, 1945, and the bombers deployed to the Marianas Islands in February.  There they joined the rest of the B-29 force attacking Japan, first with high-level precision bombing tactics, later with low-level attacks that ignited Japanese cities.

Major General Haywood Hansell, one of the air power visionaries who commanded B-29s, judged Operation Matterhorn “not a success” from the operational view.  “You just couldn’t supply B-29s over the Hump well enough to conduct a successful bombing campaign.”  In the Marianas Islands, the bombing force could be easily supplied by sea across the Pacific, now cleared of the Japanese by the island-hopping campaigns.

Hansell judged, however, that “from the standpoint of strategic effect” it was “a tremendous success,” confirming the principle of central strategic command of a bomber force rather than assignment of the forces to local commanders.  Tactical innovations pioneered in China made the Command more deadly for the remainder of the war.  Many of the obstacles to the successful strategic bombing by the B-29s were with aircraft and engines; many of these problems were shaken out in India and China.

Post-war studies demonstrated that Japan was defeated by the twin effects of the submarine campaign, which cut off its supplies, and the strategic bombing campaign, which destroyed its industrial capacity.  Operation Matterhorn was part of the latter.

Operation Matterhorn (more information)

Back as far as 1942, Roosevelt wanted to strike Japan directly with bombers, just as Germany was being by British and American strategic bombers. The USAAC had recognized this need and had already initiated programs for super heavy, very long-range bombers (the B-29 and B-32). However, even these aerial wunderkind would not be able to hit Japan from across the great distances of the Pacific.

A plan proposed by Chiang Kai-shek and Claire Chennault involved using bases around Chengtu, China, being supplied over the hump (Himalaya mountains) by air. Roosevelt pressed for this plan over the objections of most of the USAAF staff. After a variety of delays in logistics, B-29 production, and crew training, a sizable force of over 100 B-29s was sent to India as the XXth bomber command. They flew missions staging through the airbases near Chengtu for refueling. This did not work out as well as was hoped...

By late November 1944, the logistical nightmare that was the effort required to keep a sustained bombing campaign against Japan from China was deemed not worth the effort, especially since Saipan had been taken and was a better base. The 58th Bombardment Wing's operations tapered off and it moved to Tinian to join the XXIst Bomber Command.

US 20th Air Force
Bombers 4 groups operating from India B-29A

The B-29 had been originally been designed with the idea of hemispheric defense in mind. The bombers would operate out of bases in the USA and be able to hit any future enemy at long ranges to keep war well away from America's shores. In 1940, the War Department's contingency plan was changed to use 24 B-29/B-32 bomber groups to bomb Germany from bases in the United Kingdom and North Africa in case of war. However, the B-29 was destined never to be used against Germany.
Even before Pearl Harbor, President Franklin Roosevelt had been interested in providing assistance to the Chinese leader, Generalissimo Chiang Kai-shek, so that he could retaliate against Japanese air attacks on Chinese cities. Roosevelt had even proposed to transfer some USAAC B-17s to China as early as December of 1940 so that they could be used to bomb Japanese cities, but this plan had to be abandoned since there were barely enough B-17s to meet American needs. China had to be satisfied with 100 fighter planes instead. 

Immediately following Pearl Harbor, the decision was made to place emphasis on defeating the European members of the Axis first, after which the Allies would turn their full attention to Japan. After the January 1943 Casablanca Conference, President Roosevelt decided to inform Generalissimo Chiang Kai-shek that all possible aid would be sent to prevent Japan from taking over all of China. In order to do this, Roosevelt wanted to send hundreds of heavy bombers to China so that they could bring the Japanese homeland under attack. Neither the B-17 nor the B-24 had the ranges to carry out such missions, and only the B-29 could do the job. 

Up until that time, there had only been vague proposals for the mission of the B-29s. There had been some plans for B-29s to be used against Germany, with groups of B-29s to be stationed in Northern Ireland and in Egypt, but no bases had actually been constructed. Chiang wanted the B-29s sent to China right away so that they could begin an air offensive against Japan. Both General Joseph Stilwell and General Claire L. Chennault were supportive of this proposal, and exerted considerable pressure on the President to initiate such a plan. 

However, since the Japanese had cut off the Burma Road and Lido Road overland routes to China, the effort would have to be supported entirely by air. General George C. Marshall was fully aware of the enormous supply problems involved in such an effort, and was wary about diverting effort from the European theater, since the decision had already been made to win the war in Europe before diverting full effort against Japan. Nevertheless, President Roosevelt was insistent on getting help to Chiang, and suggested sending up to 300 US bombers to China. 

Things became more definitive after the August 1943 Quadrant Conference in Quebec. At that time, General Henry H. Arnold submitted a plan under which the newly-activated 58th Bombardment Wing (Very Heavy) would be stationed in the CBI Theatre by the end of 1943 and begin attacking Japanese targets by flying out of bases in China. It would be commanded by General Kenneth B. Wolfe and would consist of four groups of B-29s. It was envisaged that once sufficient numbers of B-29s were available, Japan could be forced out of the war within six months by the destruction of her war industries, making a costly seaborne invasion of the home islands unnecessary. It was projected that such a program could defeat Japan by mid-1945. 

The special B-29 project under the command of General Wolfe was given top priority in both men and materials, second only to the secret Manhattan Project. General Wolfe chose Colonel Harman as his deputy and General LaVerne Saunders was assigned as director of the B-29 crew training program. 

According to Arnold's original plan, the B-29s would be stationed permanently in China, at bases around Chengtu in the south-center of the country. Supplies of fuel, ammunition, bombs and spares would be flown in from India over the Hump. Although both the Joint Plans Committee and the Joint Logistics Committee had rejected Arnold's plan as being strategically infeasible, President Roosevelt was highly enthusiastic about the idea and passed it along to Lt. Gen. Joseph W. Stilwell, who was Chiang Kai-shek's Chief of Staff. General Stilwell pointed out that it would be impractical to carry out all of the B-29 operations from China because of the length of the supply lines, and suggested instead that the B-29s be maintained at bases in eastern India, and only staged through Chengtu in the process or aftermath of the raids on Japan. This plan had the advantage in that a complex base facility would not be needed in China, and the supply problem would be simplified if the B-29s themselves could be used to carry some of the bombs and fuel needed to build up the dumps at Chengtu. 

Although the Joint Chiefs of Staff were still skeptical about the idea, President Roosevelt was still insistent, and since FDR was the Commander-in-Chief, they had to go along. 

The British were brought into the plan, and on November 10 they agreed to provide bases for B-29 operations around Calcutta. At the same time, Chiang Kai-shek agreed to begin construction of five new airbases around Chengtu. 

On June 1, 1943, the first Superfortress unit -- the 58th Bombardment Wing (Very Heavy) had been activated at Marietta, Georgia, near Bell's Superfortress plant. On September 15, 1943, the headquarters of the 58th BW was moved to Salina, Kansas, with some of its groups near the Wichita factory. The first Superfortress wing initially had 5 groups (the 40th, 444th, 462nd, 468th and 472nd Bombardment Groups). The 472nd BG was destined to remain at Smoky Hill Field, Salina as an operational training unit, and the others were to be deployed to India. 

President Roosevelt wanted the B-29 bombing raids against Japan to start by January 1944. However, delays in the B-29 program forced General Arnold to admit to the President that the bombing campaign against Japan could not begin until May 1944 at the earliest. The crews of the B-29 needed a degree of specialist training that was not required for crews of other, less complex aircraft. It usually took 27 weeks to train a pilot, 15 to train a navigator, and 12 to train a gunner. The complexity of the B-29 was such that a lengthy process of crew integration had to take place before combat deployment could begin. By the end of December 1943, only 73 pilots had qualified for the B-29 and very few crews had been brought together as a complete team. 

Although a total of 97 B-29s had been produced by the beginning of 1944, only 16 of them were really airworthy. Most of the others were in AAF modification centers, located near the Bell-Marietta and Martin-Omaha plants and at air bases in Kansas, undergoing a series of modifications and changes necessitated by the lessons of air combat over Europe. At that time, much of the equipment and components of the Superfortress had still not been perfected, and rather than delay production by stopping the assembly lines to incorporate modifications and add new equipment, it was decided to let the first production airplanes leave the lines at Wichita deficient in combat readiness and deliver them to these USAAF modification centers to bring them up to combat standards. 

Engine fires were still plaguing the B-29 program. Some of these problems were solved by the replacement of the original R-3350-13 engines by R-3350-21 engines which did not really reduce the incidence of engine fires but at least reduced the risk of engine fires spreading to the aluminum-covered wings. The R-3350-23 was developed, but it was not ready in time to be fitted to the aircraft as they rolled off the production line, so they had to be fitted at the modification centers. 

In addition, the AN/APQ-13 bombing-navigational aid intended for the B-29 was a complex piece of equipment and was vulnerable to dirt and vibration and had to be carefully checked. Special schools had to be set up at Harvard, MIT and Boca Raton, Florida to train crews to operate the new radar set.
Alarmed at the slow pace of bringing adequate numbers of Superfortresses into service, on November 27, 1943, General Arnold set up a new organization to take responsibility for the overall control of the Superfortress units. This was to be the XX Bomber Command, to be commanded by General Wolfe. The XX Bomber Command would consist of the 58th Bombardment Wing (the command of which was transferred from Wolfe to his deputy, Col. Leonard (Jake) Harmon). The 58th BW was to initially be comprised of five groups (40th, 444th, 462nd, 468th and 472nd Bombardment Groups). 

At the same time, a new wing, the 73rd, to be commanded by Colonel Thomas H. Chapman, was added to the XX Bomber Command with four more groups to absorb the second batch of 150 Superfortresses. 

Headquarters were set up close to the B-29 factory at Wichita, Kansas. Responsibility for crew training was assigned to Col. LaVerne G. Saunders of the Second Air Force. Four airfields in Kansas (Smoky Hill, Pratt, Great Bend and Walker) were to handle this task. 

The crew training program was one of the more difficult aspects of the entire B-29 program. Because of the complexity of the B-29 aircraft, a lengthy process of crew integration was required before combat operations could begin. There was no time to start from scratch, so volunteers were called for from B-24 crews returning from operations in Europe and North Africa. Crews began to arrive at Kansas bases in November 1943, but very few bombers were ready to receive them. At that time, there was only one Superfortress for every twelve crews, and most crews had to train on Martin B-26 Marauders or Boeing B-17 Fortresses. By the end of December, only 67 pilots had managed to fly a B-29 and very few crews had been brought together as a complete team. Many gunners did not even see their first B-29 until early 1944. 

It was not until December of 1943 that the decision not to use the B-29 against Germany was finally made, and to concentrate the B-29 exclusively against Japan. However, in early 1944, the B-29s were still not ready to begin Roosevelt's promised offensive against Japan. Most of the B-29s were still held up at the modification centers, awaiting conversion to full combat readiness. By March of 1944, the B-29 modification program had fallen into complete chaos, with absolutely no bombers being considered as combat ready. The program was seriously hampered by the need to work in the open air in inclement weather, by delays in acquiring the necessary tools and support equipment, and by the USAAF's general lack of experience with the B-29. 

General Arnold became alarmed at the situation and directed that his assistant, Major General B.E. Meyer, personally take charge of the entire modification program. The resulting burst of activity that took place between March 10 and April 15, 1944 came to be known as the "Battle of Kansas". Beginning in mid-March, technicians and specialists from the Wichita and Seattle factories were drafted into the modification centers to work around the clock to get the B-29s ready for combat. The mechanics often had to work outdoors in freezing weather, since the hangars were not large enough to accommodate the B-29s. As a result of superhuman efforts on the part of all concerned, 150 B-29s had been handed over to the 20th Bomber Command by April 15, 1944. 

General Wolfe assigned the first B-29s to squadrons within the 58th Bombardment Wing and despached them immediately to India. This was a 11,530-mile journey, involving stops at Marrakech, Cairo, Karachi and Calcutta. One B-29 passed through England in March of 1944 in an attempt to confuse Axis intelligence about the intended theatre of action of the B-29, although the B-29 was never intended for use in the European theatre. Apparently neither the Germans nor the Japanese were fooled by this ploy, since the Japanese were long aware that Superfortresses were going to be based in India and staged through bases in China in an attempt to attack targets on the home islands.

The headquarters of the XX Bomber Command had been established at Kharagpur, India on March 28, 1944 under the command of General Wolfe. The first B-29 reached its base in India on April 2, 1944. In India, existing airfields at Kharagpur, Chakulia, Piardoba and Dudkhundi had been converted for B-29 use. All of these bases were located in southern Bengal and were not far from port facilities at Calcutta. All of these bases had originally been established in 1942-43 for B-24 Liberators. The conditions at these bases were poor, and the runways were still in the process of being lengthened when the first B-29s arrived. The headquarters of the 58th BW, together with the four squadrons of the 40th Bombardment Group (the 25th, 44th, 45th and 395th) were assigned to an airfield at Chakulia, the first planes arriving there on April 2, 1944. The headquarters was moved to Kharagpur on April 23. The 444th Bombardment Group (676th, 677th, 678th and 679th Squadrons) went to Charra, arriving there on April 11. The 462nd Bombardment Group (768th, 769th, 770th and 771st squadrons) to Piardoba, arriving there on April 7. The 468th Bombardment Group (792nd, 793rd, 794th and 795th Squadrons) arrived at Kharagpur on April 13. The 444th Bombardment Group later moved to a permanent base at Dudhkundi, leaving Charra to become a transport base for the C-87s and C-46s which would support the effort. 

On April 4, 1944, a special strategic command was established, to be known as the 20th Air Force, which would carry out the aerial assault against Japan. This was done at the insistence of General Arnold himself, mainly to avoid having the B-29s being diverted to tactical missions under pressure from CBI Theatre commanders such as Major General Claire L. Chennault or General Joseph Stilwell. The 20th Air Force would be commanded by General Arnold himself at JCS level. The 20th Air Force would be completely autonomous and their B-29s would be completely independent of other command structures and would be dedicated exclusively against strategic targets in Japan. For the first time, the B-29 offensive against Japan was given a name -- Operation Matterhorn. On April 10, 1944, the Joint Chiefs of Staff (JCS) informally approved Operation Matterhorn. The operational vehicle was to be the 58th Bombardment Wing (Very Heavy) of the XX Bomber Command. 

Before deployment from America, Saunders had taken over command of the 58th Bombardment Wing from Harmon. 

During the week of April 15-22, no less than five B-29s crashed near Karachi (a stop on the route to Calcutta), all from overheated engines. The entire B-29 fleet had to be grounded en route until the cause was found. The cause was traced to the fact that the R-3350 engine had not been designed to operate at ground temperatures higher than 115 degrees Fahrenheit, which were typically exceeded in Karachi. Wright engineers found that the exhaust valves on the rear row of cylinders were melting under the heat and pressure, and they designed new engine baffles to direct cooling air onto the affected areas. They also improved the flow of oil to the rear cylinders by installing crossover oil tubes from the intake to the exhaust port of the five top cylinders on both the front and rear rows. 

Modifications had also to be made to the cowl flaps. After these modifications, B-29 flights to India were resumed. 

By May 8, 1944, 130 B-29s had reached their bases in India. For the next month, the four groups flew a total of 2,867 hours of which 2,378 (83%) were on transport service, 50 on miscellaneous jobs, and only 439 in training activities, giving an average of less than 2 hours each for the 240 crews on hand.

There were four sites in the Chengtu area of China that were assigned to the B-29 operation -- at Kwanghan, Kuinglai, Hsinching and Pengshan. Construction work at these bases had begun as early as November 1943, but progress had been slow since much of the work had be done by hand. However, by May enough progress had been made that the four bases could actually be used, but the conditions were far from ideal. 

The primary flaw in the Operation Matterhorn plan was the fact that all the suplies of fuel, bombs and spares needed to support the forward bases in China had to be flown in from India over the Hump, since Japanese control of the seas around the Chinese coast made seaborne supply of China impossible. Plans were made to use transport adaptations of the B-24 Liberator (known as the C-87) in support of the operation, and to even convert Liberators into special fuel transports under the designation C-109. Many of the supplies had to be delivered to China by the B-29s themselves. For this role, they were stripped of nearly all combat equipment and used as flying tankers and each carried seven tons of fuel. The Hump route was so dangerous and difficult that each time a B-29 flew from India to China it was counted as a combat mission, calling for the painting of a camel on the aircraft's nose. 

By May 8, 1944, 148 B-29s had reached Marrakech and 230 were in India. The four bombardment groups of the 58th Bombardment Wing were assigned to their bases. 

The first action by the B-29 took place on April 26, 1944. Major Charles Hansen was flying a load of fuel to China when his plane was attacked by six Ki-43 Hayabusa fighters. The attack was beaten off, but one crew member was injured. 

The first B-29 bombing raid took place on June 5, 1944. Led by General Saunders himself, 98 B-29s took off from bases in eastern India to attack the Makasan railroad yards at Bangkok, Thailand. This involved a 2261-mile round trip, the longest bombing mission yet attempted during the war. The engines of the B-29 were still causing problems, and fourteen B-29s were forced to abort because of engine failures. The target was obscured by bad weather, necessitating bombing by radar. The formations became confused and dropped their bombs at altitudes between 17-27,000 feet rather than the planned 22-25,000 feet. Only eighteen bombs landed in the target area. Five B-29s crashed upon landing after the mission and 42 were forced to divert to other airfields because of a shortage of fuel. 

The B-29 campaign was off to a bad start, although none of the bombers were actually lost to enemy action. 

On June 6, General Wolfe received an urgent message from Washington complaining that the JCS were getting impatient and that they wanted an immediate attack on Japan proper. This attack was needed to relieve pressure from Japanese forces in eastern China where General Claire Chennault's Fourteenth Air Force airfields were under attack and to assist an "important operation" in the Pacific which was later revealed to be the invasion of Saipan. General Wolfe was caught flatfooted by this order and attempted to delay the mission until late June when he would have a larger force and more supplies in place at the forward bases in China. However, Washington demanded that he put a minimum of 70 B-29s over Japan by June 15. One of the problems was that only 86 B-29s could be equipped with the bomb-bay tanks needed for the long flight to Japan and, based upon previous experience, more than 20 of them would fail to leave the base in China while others would fail to bomb the target. But when your superiors give the orders, you do as you are told. 

By mid-June, enough supplies had been stockpiled at Chinese forward bases to permit the launching of a single sortie against targets in Japan. It was a nighttime raid to be carried out on the night of June 14/15, 1944 against the Imperial Iron and Steel Works at Yawata on Kyushu. This plant was considered to be the most important single objective within Japan's steel industry, and had long held top priority for the first strike. Intelligence estimated Imperial's annual production at 2.25 million metric tons of rolled steel -- 24% of Japan's total. The secondary target was Laoyao harbor, an outlet for much coking coal, manganese and phosphates. Because of the long distance (3,200 miles), Washington had ordered a night mission with planes bombing individually. Bombing was to be done from two levels, 8,000 to 10,000 feet and 14,000 to 18,000 feet. Two pathfinder aircraft from each group were to light off the target. Takeoff was scheduled for 1630 local time, June 15, 1944, permitting the aircraft to arrive over the target during darkness. 

Staging at the forward bases in China began on June 13, 1944 and was completed shortly before H-hour on June 15. The B-29s had left India fully loaded with bombs, requiring only refueling at the forward bases in China. Each plane carried two tons of 500-pound general purpose bombs, considered powerful enough to disrupt the fragile coke ovens by either a direct hit or by blast. Of the 92 aircraft leaving India, only 79 had actually reached China, with one plane crashing en route. The staging bases were:
             Hsinching for the 40th Bombardment Group (Very Heavy)
             Kwanghan for the 444th Bombardment Group (Very Heavy)
             Chiung-Lai for the 462d Bombardment Group (Very Heavy)
             Pengshan for the 468th Bombardment Group (Very Heavy)
Takeoffs from the forward bases in China began early in the evening (1616) and two groups approximated the schedule of two-minute intervals between takeoffs. The other two groups were slow in getting their aircraft airborne. 

Of the 75 B-29s dispatched, one crashed and four were forced to return to base due to mechanical problems. At 2338 (China time) the first B-29 over the target gave the signal "Betty," indicating "bombs away with less than 5/10 cloud." Of the 68 aircraft that had left China, only 47 attacked the intented target. One B-29 crashed in China (cause unknown), 6 jettisoned their bombs because of mechanical difficulties, 2 bombed the secondary target and 5 bombed targets of opportunity.

Unfortunately, the Japanese had been warned of the approaching raid and the city of Yawata was blacked out and haze and/or smoke helped to obscure the target. Only 15 aircraft bombed visually while 32 bombed by radar. Only one bomb actually hit anywhere near the intended target. This was a bomb which had hit a power house some 3700 feet from the coke ovens. Some damage had been done to the Kokura Arsenal, to miscellaneous industrial buildings, and to business-industrial areas. The steel industry was essentially untouched. One B-29 was lost to enemy fire and six were lost in various accidents. 

Although very little damage was actually done, the Yawata raid was hailed as a great victory in the American press, since it was the first time since the Doolittle raid of 1942 that American aircraft had hit the Japanese home islands. 

General Wolfe was ordered to keep up the attacks even in spite of a shortage of fuel and bombs at the Chengtu bases. He told his superiors that it was impossible to stage any more raids on Japan at the present time. Washington had to blame someone for the lack of progress, and General Wolfe was the most likely candidate. On July 4, the General was recalled to Washington, promoted and reassigned. He was replaced on a temporary basis by Brig. Gen. LaVerne G. Saunders until a permanent commander could be found. 

On July 7, while under temporary command of General Saunders, eighteen B-29s attacked targets at Sasebo, Nagasaki, Omura and Yawata with ineffective results. On July 9, 72 B-29s hit a steel-making complex at Anshan in Manchuria. Of the 72 aircraft launched against Anshan, one crashed on takeoff and eleven suffered mechanical failures en route to Manchuria and had to abort. Four aircraft were lost and results were poor. On the night August 10/11, 56 B-29s staged through British air bases in Ceylon (now known as Sri Lanka) attacked the Plajdoe oil storage facilities at Palembang on Sumatra in present-day Indonesia. This involved a 4030-mile, 19 hour mission from Ceylon to Sumatra, the longest American air raid of the war. Other B-29s laid mines in the Moesi River. At the same time, a third batch of B-29s attacked targets in Nagasaki. These raids all showed a lack of operational control and inadequate combat techniques, drifting from target to target without a central plan and were largely ineffective. 

Many of the accidents which plagued the B-29s operating out of China and India were caused by engine fires, which were still a problem in spite of massive efforts to correct them. The cylinder head temperature gauges were red-lined at 270 degrees Celsius. The combination of very high ambient ground temperatures (100 to 115 degrees Fahrenheit) and the inadequate cooling system of the engines would often result in head temperatures exceeding 310 during and immediately after takeoff. The high temperatures often resulted in the evaporation of valve stem lubrication, which could cause the valve to break off. The broken valve would then blow the cylinder off, which inevitably resulted in a fire. 

Crews soon learned that the key to keeping the engine head temperature within tolerable limits was to have as much airspeed as possible when they became airborne on takeoff. During takeoff, they used the entire runway and reached a speed of 140-145 mph to become airborne in a fairly nose-low attitude. After takeoff, they would stay fairly low for a rather long time, with no effort to climb. This was done to attain the climbing speed of 200 mph as rapidly as possible. As the airspeed built up, the flight engineer would start to squeeze the large cowl flaps closed, since the key to controlling the head temperatures was airspeed, and as the speed got higher, cowling flaps in the extended position produced more drag than cooling. 

General Wolfe's replacement was Major General Curtis E. LeMay, who arrived in India on August 29. General LeMay was only 38 years old and was the youngest major general in the Army. He had earned a good reputation as commander of a B-17 air division in Europe. He was known as a tough, Patton-type of commander and had a "take-charge" reputation. As a start, he stepped up the frequency of B-29 missions and intensified the training of combat crews. He replaced the four-plane diamond formation with one of twelve aircraft grouped in a defensive box. He introduced the concept of lead crews who would be responsible for finding and marking the target. In the future, both the bombardier and radar operator would control the bombing run, so that whoever had sight of the target at the critical moment in the bomb run could release the bombs. At the same time, the 58th Bombardment Wing was reorganized, and the junior squadron from each group (the 395th, 679th, 771st and 795th) was disbanded. This left each group with three squadrons of ten B-29s each. 

It took a while for these changes to have an effect. Another raid against Anshan in Manchuria on September 26 was inclusive. An attack on October 25 on the Omura aircraft factory on Kyushu showed better results, particularly in the decision to use a two-to-one mixture of high-explosive and incendiary bombs. A raid was carried out on November 11 against the Chinese city of Nanking, which had been occupied by the Japanese since 1937. Supply problems and aircraft accidents were still preventing a fully effective concentration of force and effort. In addition, Japanese defensive efforts were becoming more effective. On November 21, six B-29s were destroyed by Japanese aircraft during a raid on Omura. A similar loss rate occurred on December 7 over the Manchurian Aircraft Company plant at Mukden. B-29 losses to accidents, enemy interception, and to Japanese air attacks on the Chengtu forward bases soon came to be prohibitive, and by the end of 1944 had reached 147. 

LeMay gradually cut back on the number of missions flown out of the Chinese bases in favor of missions to Singapore, Borneo, Malaya and Sumatra that could be flown from the bases in India where the supply situation was much more favorable. 

By late 1944, it was becoming apparent that B-29 operations against Japan staged out of bases in Chengtu were far too expensive in men and materials and would have to be stopped. In December of 1944, the Joint Chiefs of Staff made the decision that Operation Matterhorn would be phased out, and the 58th Bombardment Wing's B-29s would be moved to newly-captured bases in the Marianas in the central Pacific. 

The last raid out of China was flown on January 15, 1945, which was an attack on targets in Formosa. The 58th Bombardment Wing then withdrew to its bases in India and was redeployed to the Marianas in February. 

During Operation Matterhorn, 49 separate missions had been flown involving 3058 individual aircraft sorties. Only 11,477 tons of bombs had been dropped. In spite of the massive effort involved in Operation Matterhorn, only insignificant damage had been done to targets in Japan. 

In retrospect, Operation Matterhorn had been a failure. The supply problems proved to be insoluble, and the Chengtu bases in China were too far west, requiring long overflights of Japanese-occupied territory in China before the Japanese home islands could be reached. Even then, only the southernmost Japanese island of Kyushu was in range of the B-29s. Nevertheless, the Matterhorn operation provided valuable experience for the B-29 operations that were to be mounted from the far more convenient bases in the Marianas. 

Order of Battle of XX Bombardment Command:
58th Bombardment Wing - activated June 1944
40th Bombardment Group
25th, 44th, 45th, 395th Bombardment Squadrons, 395th deactivated September-October 1944.
444th Bombardment Group
676th, 677th, 678th, 679th Bombardment Squadrons, 679th deactivated September-October 1944.
462nd Bombardment Group
768th, 769th, 770th, 771st Bombardment Squadrons, 771st deactivated September-October 1944.
468th Bombardment Group
792nd, 793rd, 794th, 795th Bombardment Squadrons, 795th deactivated September-October 1944.
The initial plan of use, implemented according to the guidelines of the US President Franklin D. Roosevelt, resulting in promises made to China and calls Operation Matterhorn, was to use the B-29 to attack Japan and other objectives as needed, starting from four forward bases in Guangxi, the southern region of China and five airports, to be used as main bases, in India, in the region of the current Bangladesh.

The region of Chengdu was finally preferred to that of Guilin to avoid having to train 50 Chinese divisions to protect the bases against attacks terrestrial Japanese.

This project was extremely expensive, because there were no land links between India and China and all materials necessary for the operation of the forward bases had to be transported by air passing over the Himalayas through transport aircraft, or with the same B-29, using some specimens which were taken off the guards and weapons to turn them into aircraft for the transport of fuel.
The B-29 began to arrive in India in early April 1944.

The first flight of B-29 transfer from airports in China over the Himalayas, bypassing the so-called The Hump, took place April 24, 1944.

The first combat mission of the B-29 was launched June 5, 1944: 77 of the 98 B-29 departed from bases in India and were sent to bomb the railway workshops in Bangkok in Thailand.

Five B-29s were lost due to technical problems.

On June 15, 1944, 68 B-29 took off from bases in Chengdu in China and 47 aircraft reached and bombed the imperial Yawata steelworks in Japan.

This was the first bombing raid on the Japanese islands from Doolittle in April 1942.

In this mission, we were the first combat casualties of B-29, with one aircraft destroyed on the ground by Japanese fighters after an emergency landing in China, one lost because of anti-aircraft fire on Yawata, and another plane, the Stockett's Rocket (named after Captain Marvin M. Stockett, the commander of the aircraft) disappeared after takeoff from Chakulia in India.

The raid caused little damage to the lens, with a bomb that struck installations and practically ran out of fuel reserves of the bases of Chengdu, causing slow operations until stocks were not replenished.
Against the B-29 was also adopted by the Japanese tactic of launching intentionally with fighter bombers trying collision.

The first example of this technique was recorded during the raid of August 20 against the steel mills of Yawata.

Sergeant Shigeo Nobe the 4th Sentai intentionally flew with his Kawasaki Ki-45 against a B-29; scrap projected by the explosion, severely damaged another B-29 that crashed.

The two US losses were the B-29 freshman B-29-10-BW 42-6334 Gertrude C with commander Colonel Robert Clinksale and the B-29 freshman B-29-15-BW 42-6368 Calamity Sue with Commander Captain Ornell Stauffer, both of the 486th BG.

Many of these aircraft were destroyed in such attacks in the following months.

Although the term "Kamikaze" is used to identify this type of attack, the word is not used by the Japanese historiography distinguishes between suicide attacks to ships and combat aircraft of this type, not necessarily suicide.

The B-29 were withdrawn from the airports in China towards the end of January 1945.
In the period of use of these aircraft departing from China and India, were conducted missions against many targets across South East Asia, but it was decided the gradual transfer of the entire fleet to new bases in the Mariana Islands.

The last mission departing from India, was launched March 29, 1945.

In addition to the logistical problems associated with operations starting from China, the B-29 could reach only a limited part of Japan, starting from those bases.

The solution to this problem was the conquest of the Mariana Islands that would bring goals as Tokyo, 2400 kilometers away, within the "Superfortress".

It was therefore decided in December 1943 to win the Marianas.

The Marianas operation was starting to go the same way as Operation Matterhorn, with losses being high and not much damage to the enemy being done. Hansell strove to improve the skill of his bombardiers and lead crews, who seemed to be far too eager to resort to radar when conditions were unfavourable. However, it could be said that they did have good reason - one hindrance to bombing was restricted vision through iced-up windows, necessitating new heating devices.

Though dissatisfied with the early performance of his Command, Hansell seems to have considered this as an experimental period. Not so Arnold, who was no doubt apprehensive of the Joint Chiefs of Staff view if the expensive programme did not soon produce tangible evidence of success. The war in Europe might soon be concluded, when the full weight of Allied power would be shifted to the Pacific with an invasion of the Japanese home islands. If the B-29s were to make this unnecessary by bombing Japan into submission, there was need of immediate improvement.