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While U.S. submarines were destroying the Japanese merchant fleet on the high seas around Japan, Tokyo used the shallow Sea of Japan as a secured lake against them. The Japanese mined the narrow entrances to the sea, which allowed Japanese shipping to continue to bring vital supplies to Japan from the Korea Peninsula without the constant fear of attack. That all changed in June 1945, when nine U.S. submarines entered the Sea of Japan through the Tsushima Straits and sank twenty-eight Japanese ships at the cost of one American submarine.
To reduce further Japanese shipping, B-29s mined the Korean ports of Pusan, Seisen, and Rashin forcing the Japanese to move materials by rail to less functional ports. American submarines thus had a devastating impact of Japanese lines of communication and were a vital component of America’s strategy to the defeat of Japan.6 As U.S. submarines sank Japanese ships at will, the U.S Pacific Fleet was conducting operations against the remaining Japanese warships and against key coastal targets. In July 1945, Admiral William Halsey sent Task Force 38, comprised of three battle groups built around fourteen aircraft carriers, to conduct a series of air attacks and naval bombardments against Japan. The carrier planes focused their strikes on coalmines and transportation facilities in northern Honshu and Hokkaido. These strikes caught northern ports “clogged with shipping diverted from mined harbors to the south,” and sank along with their vital coal cargo. Further strikes destroyed the inter-island rail and sea system that moved the coal to Japanese industries.
These attacks by Halsey’s planes proved to be the “most devastating single strategic-bombing success of all the campaigns against Japan.”7 The second part of Halsey’s plan was to have the fleet’s battleships bombard Japanese coastal targets, while Task Force 38 concentrated on destroying the remaining warships in the Richard B. Frank, Downfall: The End of the Imperial Japanese Empire, pp. 154 - 156.
Ibid., p. 157.
Imperial Navy. During the last month of the war, Halsey’s battleships fired thousands of sixteen-inch shells into several Japanese coastal cities and his carrier planes sank or damaged the remainder of Japan’s battleships, heavy cruisers, and aircraft carriers. Besides the destruction of the Japanese fleet and Japan’s coal facilities, the attacks on the Japanese homeland had two additional effects. They allowed the Soviet Navy greater access to the Sea of Japan without interference from the Imperial Navy and, more importantly, the Japanese people saw first hand that their military could not stop the American advance. Except for the constant aerial bombardment and the relentless fire bombing of their cities, the Japanese did not experience the full power of the American offensive. However, once American warships tightened the blockade and appeared off shore to fire directly onto the Japanese coast, the realization that the war was lost spread throughout Japan.8 To make the naval blockade more effective, the American military had to destroy Japanese war industries and, in that regard, the biggest obstacle was the Pacific Ocean. After the swift Japanese victories in 1941 and 1942, the United States no longer had air bases within striking distance of Japan. The only option at first was to build bases in China and conduct limited strikes against Japanese targets. Major General Claire L. Chennault was the driving force behind the plan for “early sustained bombing of Japan,” called Operation MATTERHORN. The first B-29 bases were ready to conduct operations in June 1944, under the control of the XX Bomber Command but early results were meager. The B-29s could only a payload of only “twotons” of bombs, and flying at night or high altitudes hitting targets difficult. Because of the tremendous logistical requirements to sustain the B-29s in China and their ineffectiveness against targets in Japan, American planners turned to the Marianas as an operating base for the B-29s.9 Ibid., pp. 158 – 159.
Allen, Codename Downfall, pp. 80 – 81.
The fall of the Mariana Island in June 1944 provided the United States with valuable bases within striking distance of Tokyo. More importantly, these bases were safe from Japanese attacks and easily resupplied by cargo ships. The XXI Bomber Command, commanded by Major General Haywood S. Hansell, began missions against Japan in October 1944. The early attempts to bomb Japan from the Marianas proved just as ineffective as the China based B-29s.
Hansell continued the practice of conducting so-called high-altitude precision bombing even after these tactics had not produced acceptable results. In addition to the losses caused by maintenance problems and enemy action, the B-29 missions failed because Hansell had “poor intelligence about Japanese industry and lacked maps.”10 Japanese authorities, moreover, dispersed the industrial equipment and machinery throughout the nearby cities to limit the effects of the bombings. “The line between military and civilian, residential, and industrial was often non-existent.”11 From 30,000 feet, furthermore, pilots seldom had visual sighting of the target, radar was useless, and the high winds at that altitude scattered B-29’s formations. His successor, General Curtis LeMay, assumed command in January 1945, and continued to use the same tactics, with equally unsatisfactory results.12 A few weeks into his mission, LeMay realized that he would have to change tactics.
LeMay decided that low-level incendiary raids against Japanese cities was only way to destroy their production capabilities. LeMay had no illusions: this was a shift from precision bombing to area, or saturation bombing. The ordinance of choice was the newly invented MK-69 incendiary bomb, filled with “jellied gasoline” called napalm. These 6lbs bombs were small and stuck to everything they touched. To increase accuracy and bomb payloads, LeMay ordered his pilots to fly between 5,000 and 8,000 feet. He also had all the machine guns removed from the bombers, Ibid., p. 82.
Ibid., p. 197.
Paul D. Walker, Truman’s Dilemma: Invasion or the Bomb, pp. 192 -196.
since the missions were at night and the capabilities of the Japanese night fighters were poor, and that allowed the B-29s to deliver more incendiary bombs on each mission. The first of these deadly raids occurred in March 1945 with the fire bombing of Tokyo. LeMay’s bombers dropped 1,665 tons of incendiary canisters and high explosives from 279 B-29s, which created a tremendous firestorm that burned a large area of Tokyo. These raids became the template for further raids on more Japanese cities.13 The primary mission of the XXI Bomber Command was the destruction of Japanese cities. Following the all out incendiary raids in March 1945, LeMay had to terminate his operations temporarily because he “literally ran out of bombs,”14 but when the ordinance became available, he resumed the incendiary raids. On the nights of May 25-26, 1945, his bombers struck a large area in Tokyo that housed residential, industrial, commercial, and military targets.
The results were devastating as strong winds spread the firestorm through twenty square miles of the city, destroying the symbols of Japanese imperialism. Among the destroyed government buildings were the War Ministry, Navy Ministry, Army General Staff Headquarters, official residence of the war minister, Transportation Ministry, and the Greater East Asia Ministry. The greatest impact was that the bombing destroyed the Imperial Palace, and barely missed the Emperor and Empress. Throughout the American bombing campaign, the Japanese believed “that the Imperial Palace was immune from the foe; few had believed that its survival until 25th May was attributed to sheer luck.”15 By mid-June 1945, the B-29s had exhausted the original list of targets on the “Selected Urban Industrial Concentrations” by destroying or damaging these urban areas. The capture of Okinawa by U.S. forces on June 21, 1945, allowed the XXI Bomber Command to expand its Frank, Downfall, pp. 62 - 67.
Ibid., p. 69.
Ibid., pp. 74 - 75.
campaigns to the entire Japanese homeland. LeMay targeted cities that would burn easily, cities that had a direct effect on Japan’s war industry, and transportation facilities. During the last two months of the war, U.S. bombers completed the destruction of Japan’s petroleum industry, chemical industries, aircraft plants, and ball-bearing plants. To help reduce civilian casualties and cause psychological effects, LeMay began dropping leaflets on potential targets prior to a raid. The idea was to show the residence of targeted cities that “America was not fighting the Japanese people.” The number of civilian casualties dropped significantly in cities that received leaflet drops.16 While the naval blockade and aerial bombardment devastated Japan’s war economy, American planners were busy studying a possible invasion of the Japanese mainland. As early as April 1943, the U.S. Joint War Plans Committee produced a draft plan, JWPC 15, that only confirmed what the Joint Chiefs of Staff had decided, that to achieve “the unconditional surrender of Japan might require actual invasion of the Japanese homeland.” JWPC 15 centered primarily on defeat of the Japanese Army in Eastern China, where the United States would establish bases to bomb Japan, and had an established naval blockade. However, the “demonstrated impotence” of the Chinese troops against the Japanese concerned American planners that an invasion would have to come from across the Pacific, since the Japanese would maintain control of the Asian coast. In November 1943, U.S planners presented the Chiefs of Staff with a strategy to defeat Japan that called for the invasion of Hokkaido in 1945 and Honshu in early 1946. To support the invasion of Japan, planners recommended that Admiral Nimitz receive priority in support for the capture of the Mariana Islands “for use as strategic bomber bases to pound Japan” and that General MacArthur continue his drive toward the Philippine
Islands. None of the U.S. senior military leaders liked the plan. However, they agreed, “that the proposed plan to defeat Japan had to be reconsidered.”17 Since America’s entry into World War II, its strategic priority had been the European Theater and defeating Nazi Germany. The last German offensive in the winter of 1944 caught the Allied planners by surprise, which forced the United States to flood Europe with reinforcements to replace the sudden losses in troops and equipment. Material and personnel projected for the Pacific Theater went directly to Europe, while planners in the Pacific delayed the assault on Japan. During the Yalta Conference in February 1945, General Marshall and Admiral King presented President Roosevelt and Prime Minister Churchill with a revised plan that called for the invasion of Kyushu, rather than Hokkaido, with a follow-on assault on Honshu. Both operations depended heavily on the defeat of Germany and the redeployment of troops and equipment.18 The planning for the invasion of Japan was unlike that for any of the previous operations against the Japanese. This time American soldiers and marines would invade Japanese soil and fight an enemy that had already proven its willingness to fight to the last man, women, and child.
Military planners saw in the recent battle of Okinawa, 350 miles away from the Japanese islands, an indication of how the Japanese would defend their homeland. The mobilization of the civilian population on Okinawa showed that the invasion force would face not only the stubborn Japanese military, but a potentially hostile population as well. It was clear to the planners that “Japan had plenty of fight left in her and that surrender was still not an option.”19 On May 25, 1945, the Joint Chiefs of Staff sent the operational plan Operation DOWNFALL, the invasion of Japan, to General MacArthur, the Commander in Chief U.S.
Allen, Codename Downfall, pp. 129 - 132.
Ibid., pp. 134 – 135.
Walker, Dilemma, p. 149.
Army Forces Pacific and to Admiral Nimitz, the Commander in Chief U.S. Pacific Fleet.
DOWNFALL was to be a two-phased operation consisting of Operation OLYMPIC, the invasion of Kyushu, and Operation CORONET, the invasion of Honshu. The U.S. Sixth Army received the mission to conduct the amphibious and ground operations, with a target date of November 1,
1945. The primary tasks of the Sixth were to “seize and occupy southern Kyushu as far north as the general line Tsuno-Sendai; establish air forces and naval facilities for support of the CORONET Operations.”20 MacArthur’s intent was to secure only the southern third of Kyushu, which was enough to construct airfields, improve ports and to build a base of operations to support the CORONET phase of the operation. The Sixth Army’s ground forces consisted of 650,000 soldiers and marines organized into three corps that would land on three beachheads at Miyazaki, Ariake Bay and Kushikino.21 Military planners projected March 1, 1946, as the date for the opening of second phase of Operation DOWNFALL to begin. The invasion of Honshu was the decisive effort that would force the Japanese into accepting unconditional surrender. Operation CORONET planned for the largest invasion force ever assembled, which included the entire U.S. Marine Corps, the U.S.
Navy in the Pacific, four U.S. Air Forces and three armies that totaled over 1.5 million personnel. Due to the magnitude of the operation, MacArthur designated the U.S. 1st, 8th, and 10th Armies as the army headquarters responsible for the planning and execution of the invasion.
The primary task the commanders received was “to destroy hostile forces and occupy the TOKYO-YOKOHAMA area.”22 Like the invasion of Kyushu, MacArthur intended to secure what was necessary to establish a base of operations on Honshu. It would reinforce the blockade and provide a platform for future operations, and permitting American forces to “block off the Steven T. Ross, U.S. War Plans: 1938-1945, pp. 362 – 363.
Frank, Downfall, pp 118 - 121.
Ross, War Plans, p. 365.