Operation Olympic. It would be an amphibious landing a third larger than D-Day in Normandy. The expectation was that nine US divisions would be opposed by three Japanese divisions. In fact, Japan had 14 divisions on Kyushu.
Far East Air Forces would support the invasion with 10 fighter groups, six heavy bomb groups, four medium bomb groups, four light bomb groups, three reconnaissance groups, and three night fighter squadrons.
In addition, the Bs would continue their strategic bombardment. Operation Coronet. This was the code name for an invasion, in March , of Honshu, the largest of the Japanese islands. Coronet would require 1,, US troops, including a landing force of , soldiers and marines. It would be the largest invasion force ever assembled. Operation Coronet would make use of airfields on Kyushu captured during Operation Olympic. Surrender was dishonorable. Defeated soldiers preferred suicide to life in disgrace.
Those who surrendered were not deemed worthy of regard or respect. On Kwajalein atoll, the fatality rate for the Japanese force was On Saipan, nearly 30,—97 percent of the garrison—fought to the death. On Okinawa, more than 92, Japanese soldiers in a force of , were killed. Japan continued the fight with fanatical determination in the belief that the willingness of soldiers and sailors to sacrifice their lives would compensate for shortfalls in military capability.
Some 17 million persons had died at the hands of the Japanese empire between and , and more would be certain to die during the final stand. Japan had been controlled by the military since the s. Members were the prime minister, foreign minister, Army minister also called War Minister , Navy minister, chief of naval general staff, and chief of the Army general staff.
Army and Navy ministers were drawn from the ranks of serving officers. Korechika Anami. Emperor Hirohito, regarded as divine and revered as the embodiment of the Japanese state, was supposedly above politics and government.
In fact, he was interested in, and well-informed about, both of them. His enthusiasm for the war did not wane until the bombs and hardship reached Japan. On March 18, Hirohito toured the areas of Tokyo firebombed March 9 and 10; he concluded that the war was lost and that Japan should seek an end to it as soon as possible. However, Hirohito agreed with the strategy of waiting to negotiate until Japan won a big battle, strengthening its bargaining position.
Japan still held most of the territory it had captured in Asia and Indochina, and hoped to keep some of it. Its remaining military strength was considerable. If it could inflict painful casualties on the United States, Japan might be able to secure favorable terms, it thought. Today, a fierce argument still rages about what the casualty toll might have been if the Operation Downfall invasion had taken place.
The answer is elusive. Wartime casualty estimates were based on inaccurate assumptions—usually low—about enemy strength. Postwar analysis has been severely distorted by academicians and activists on the American left seeking to prove that neither an invasion of Japan nor the atomic bomb was necessary to end the war.
There is no independent evidence of what Marshall said at Potsdam. Truman may have been embellishing it, but his numbers were not preposterous, as is often alleged. In fact, Joint Staff planners on two occasions worked up casualty estimates and came out in the same range.
An April report projected casualties of 1,,—including , killed and missing—in Operations Olympic and Coronet, and more if either of the campaigns lasted more than 90 days.
At a critical White House meeting on June 18, Marshall gave his opinion that casualties for the first 30 days on Kyushu would not exceed the 31, sustained in a similar period of the battle for Luzon in the Philippines.
Marshall took that number from an inaccurate report. Casualties for the first 30 days on Luzon had been 37, Others at the meeting based their estimates on Okinawa, where US casualties were about 50, Also, in view of the fact that these troops must be maintained principally by the Kurume and Kumamoto Depots, the roads and rail lines have undoubtedly become vital supply lines.
Concern of the Japanese as to the continuity of these overland lines of communications and recognition of their vulnerability to air bombardment is emphasized by recent initiation of Special AA Defense measures Laborious passage of blocked defiles and long overland marches would be required It is probable that the Japanese may resort to night barge movement.
An ample supply of small coastal craft is available and their tactics have long stressed the use o f this means of troops transport Effective air and sea control should limit if not prevent the use of this method The rate and probable continuity of Japanese reinforcements into the Kyushu area are changing the tactical and strategical situation sharply.
There is a strong likelihood that additional major units will enter the area before target date; we are engaged in a race against time by which the ratio of attack-effort vis-a-vis defense capacity is perilously balanced. The Japanese have correctly estimated Southern Kyushu as a probable invasion objective, and have hastened their preparations to defend it. They have fully recognized the precarious nature of the land and sea routes by which they must concentrate and support their forces in Southern Kyushu.
They are vigorously exploiting available time to complete the deployment and supply lines of strong forces in the area before they are deprived of the full use of their limited lines of communication.
Since April , enemy strength in Southern Kyushu has grown from approximately 80, troops including in mobile combat the equivalent of about 2 Infantry Divisions to an estimated , including 7 divisions and 2 to 3 brigades, plus Naval, Air- Ground, and Base and Service Troops.
This rapid expansion within a few weeks' time, supply of this. It is also probable that some o f the new units identi fied in Southern Kyushu are not yet fully assembled and that at least one division the th which was probably formed of local volunteers has not yet been completely equipped. The assumption that enemy strengths will remain divided in North and South Kyushu compartments is no longer tenable.
The trend of reinforcements from North to South Kyushu is unmistakable. Increasing air raids by American bombers against southern Kyushu and Shikoku in June gave the Japanese another reason to believe that these areas would be the focal point for the initial invasion of the Homeland.
Accordingly, Imperial General Headquarters hastened operational preparations in those areas and gave urgent priority to transporting and accumulating supplies to support the newly organized ground forces of southern Japan.
Shifting the emphasis of defense to Kyushu necessitated a postponement of military preparations in the Tokyo-Yokohama area. The Japanese feared that if the invasion of the Kanto region should be initiated immediately after the Kyushu attack, or if Honshu should be assaulted directly, an adequate defense could not be made since most of the Japanese air and naval power would already have been committed to Kyushu. For this reason, Imperial General Headquarters were reluctant to transfer ground strength from the capital city area until the very last moment.
Although air and sea preparations were being pushed in Kyushu, and supplies and munitions were being moved southward, the Japanese. They assumed correctly, however, that the first aim of the United States would be the annihilation of the Japanese forces on the southern Kyushu front and the occupation of strategic air bases and harbors in Miyazaki and Kagoshima Prefectures.
Following the invasion of Tanega Shima, where a fighter base would be installed, it was considered probable that the American forces would direct their main attack against the Shibushi area on the Ariake Bay front and the Sumiyoshi coast on the Miyazaki Plain.
A secondary attack was expected on Fukiagehama on the Satsuma Peninsula. Since these three areas were geographically cut off from each other, it was believed that the Americans would seek to divide and contain the Japanese units therein. The Japanese, therefore, estimated that the first attack would be against either the Miyazaki Plain or the Satsuma Peninsula, or both.
The main force of the assault would then in all likelihood be directed at Ariake Bay while other elements would attempt to break through the mouth of Kagoshima Bay. Simultaneously with these attacks by ground forces, an airborne landing would possibly be made on the airfields around Kanoya and Miyakonojo. It was also thought probable that the Tosa Plain of southern Shikoku would be invaded to destroy the launching places of Japanese special-attack planes and, at the same time, establish American fighter bases.
It was anticipated that the United States would employ about 15 divisions, with 10 or 12 divisions attacking southern Kyushu. Two divisions, according to Japanese estimates, would be committed to Shikoku and the rest to strategic reserve. The initial landing force, which was expected to be sufficiently strong to defeat a Japanese counterattack, would probably comprise at least 3 divisions in the main sector and about 2 divisions on the other fronts.
To counter the expected United States invasion of southern Kyushu, plans were made to attack the main body of the landing force on the sea and in the coastal landing areas. The entire air strength in the Kyushu area would be employed against the invasion convoys. Reconnaissance was to be conducted on a day and night basis along a mile radius of the Homeland by naval reconnaissance planes augmented by army air reconnaissance elements.
Secret airfields would be utilized by suicidal special-attack units to escape bombing raids. To conserve air strength for employment against the landing forces, carrier task forces supporting the invasion would be attacked by only a few hundred planes and then only when it became unmistakable that a full-scale invasion was in progress. The bulk of the air fleet of 10, planes, mostly of the small special-attack type, would be launched against the warships and transports in the crucial invasion area.
Japanese plans called for these planes to be completely expended within a ten-day period in a supreme effort to repel the invasion forces.
By the end of June , 8, of the necessary craft were already available; the other 2, were expected to be finished by Fall.
The Japanese Navy had little power left to oppose an Allied assault. Its remaining forces consisted of a variety of small underseas special-attack craft and a few heavy surface units that had been hidden from Allied attack. The total destroyer strength of nineteen operational ships was to be distributed along the islands of the Inland Sea. As soon as the invasion convoy entered its anchorage, the destroyers would attack in co-ordination with air force planes and surface and underwater special-attack units.
About thirty-four submarines of all types were available for patrol duty and harassment of Allied convoy and supply lines. The surface special-attack forces, in conjunction with air and other naval units, were ear-marked for strong mass assaults on American transports in the invasion area.
Midget submarines Koryu would strike at the convoy before and after its entrance into the anchorage. Land preparations on Kyushu in June and July were largely inadequate and an Allied assault at that time would have found Japan's defenses generally incomplete.
In their planned policy of playing for time, the Japanese were aided by the strong resistance on Okinawa, which they felt would further delay the invasion date. Utilizing this needed interval, the Japanese implemented their operational plans and hastened to complete all defenses and to co-ordinate all activities for the objective of "annihilating the enemy on the beaches through offensive action.
Responsibility for the defense of the Kyushu area was assigned to the Sixteenth Area Army with headquarters at Fukuoka. Under its command were the Fortieth, Fifty-sixth, and Fifty-seventh Armies each the equivalent of an American corps , one independent line-combat division, four independent coastal-combat brigades, and miscellaneous service units. The Fifty-sixth Army occupied northern Kyushu, with most of its strength distributed along the northwestern coast from Moji to Sasebo.
The Fifty-seventh Army was responsible for the defense of the southeast and was concentrated in the Miyazaki Plain region. The total strength assigned to the immediate defense of Kyushu amounted to approximately 7 line-combat divisions, independent mixed brigades, and 3 tank brigades.
The Japanese tactical plan called for a rigid defense of the beaches which would be reinforced as rapidly as units could be sent from other parts of Kyushu and the western regions of Honshu. The ridges immediately to the rear of the anticipated landing areas were fortified by a network of large caves and tunnels covered by a series of strong artillery and mortar emplacements and manned by large forces of coastal-combat ground troops.
These troops would meet the first assault waves and, together with the line-combat divisions, would endeavor to hold all positions until the arrival of the mobile reinforcements at the beach battleground. If the primary target of the Allies could be ascertained before the landings, then the main Japanese forces would rush to that point. If the Allied target should be unclear or if all points should be invaded simultaneously, then the main enemy strength would be committed to Ariake Bay, while delaying actions were fought on other fronts.
In all cases, the decisive engagement would be waged in the beach areas with all available forces moving toward the southern Kyushu coasts. The whole object of the Japanese was to repel the invaders before they could put their heavy armor and artillery ashore. The Japanese realized that their defense plans contained numerous weak points but their situa-. Four months after the first American troops had fought their way ashore on Kyushu, the next and decisive amphibious operation against Japan would be launched.
Two armies, the First and the Eighth, were charged with the second mammoth assault against the heartland of Japan. Their immediate mission was to destroy all opposition and occupy the Tokyo-Yokohama area.
General MacArthur would exercise personal command of the landing forces and direct the ground operations on the mainland. With him would be the advance echelon of his General Headquarters to act as the Army Group Headquarters in the field. Operation "Coronet" would be supported by all army and navy forces in the Pacific and, in addition, would be augmented by numerous combat units redeployed from Europe.
Air, naval, and logistic support was outlined along the same general pattern as "Olympic" except on an enlarged scale. The initial landings would be staged by 10 reinforced infantry divisions, 3 marine divisions, and 2 armored divisions. Launched from the Philippines and Central Pacific bases, the attacking forces would be constantly protected by ships and planes of the Pacific Fleet as well as by land-based aircraft.
Thirty days after the initial assault, each army would be reinforced by a corps of 3 divisions. These 25 divisions were to seize the Kanto Plain, including the general areas of Tokyo and Yokohama, and then carry out any additional operations necessary to break Japanese resistance.
Strategic reserve for the entire operation would consist of a corps of 3 divisions located in the Philippines and a sufficient number of divisions from the United States to permit reinforcement at the rate of 4 per month.
The amphibious assault against Honshu would be preceded by heavy blows of Allied naval and air forces against the Japanese Empire. Carrier planes from the Pacific Fleet would co-operate with the Strategic Air Force in carrying out repeated attacks against vital areas of the Japanese Home Islands to strangle land and sea communication and wipe out selected targets ashore. Land-based planes from newly won fields in Kyushu together with fighters and bombers from Okinawa would continue to range over the Empire and the Asiatic coast, destroying any remaining enemy aircraft, shattering land communications, and reducing defensive installations.
All air attacks would be intensified as the landing date approached, culminating in an all-out effort, co-ordinated with naval bombardment, during the last fifteen days. At the same time, subsidiary actions in other theaters of operations would be aimed at containing Japanese air and ground forces. The China Theater would conduct neutralizing air and ground attacks against the enemy on the Asiatic mainland.
The Southeast Asia Command would launch similar operations in the. Naval and air forces based in the Aleutians would be called upon to lend general support wherever possible. All plans were directed toward the successful execution of the greatest amphibious operation ever planned. The decisive operation in the projected campaign to bring about the final collapse of Japan was the invasion of Honshu.
In the event that the campaign in the Kanto Plain did not prove to be the last battle, the secondary objective would be achieved-secure positions from which to continue air, ground, and amphibious operations in the main islands of Japan. The choice of the Kanto Plain for the final campaign in the Japanese Homeland had several distinct advantages.
Firstly, that area offered a wide choice of suitable landing beaches-a cardinal consideration in any amphibious operation. Logistic requirements to support the large forces involved necessitated good port facilities; the western shores of Tokyo Bay offered the best in Japan.
In addition, the Kanto area served as the political and communications center for the Japanese Empire, containing approximately 50 per cent of Japan's war industry. Geographically, the Kanto Plain extends approximately 80 miles north and south and 70 miles east and west, covering between 5, and 6, square miles.
The north and west sides are bordered by the mountainous masses of central and northern Honshu, which rise sharply to heights of 1,, feet. Its eastern side is bounded by the Pacific Ocean and its southern side, by the waters of Tokyo and Sagami Bays. These are the Kashima and Kujukuri beaches on the east coast, and Sagami beach at the head of Sagami Bay.
From each of these landing points, fairly good routes lead into the Kanto Plain. They wanted to use air bases in China and Korea to launch bombing raids against key cities in Japan.
The army believed that such a campaign would take too long and that the morale of the American public might suffer as a result. They supported the use of an invasion that would go to the heart of Japan — Tokyo. The army got its way.
It quickly became apparent that any invasion of Japan would present huge difficulties. There were very few beaches that could be used as a landing place and the Japanese knew this. Both sides knew that only the beaches in Kyushu and the beaches at Kanto, near Tokyo, could support a huge amphibious landing. The Japanese took the appropriate measures in both areas. The Americans had planned to land in Kyushu first and use it as a base for planes to attack other targets in Japan.
Although Japan still had 4 million men under arms, well over half were essentially trapped in China and Manchuria thanks to the U. Navy, especially submarines and unavailable for the defense of the Japanese Home Islands. Nevertheless, in over two thousand years, Japan had never been successfully invaded.
The most serious previous threat came from two Mongol invasion attempts in and , both of which were thwarted by typhoons that caused massive ship and manpower losses. By , the Japanese had made extensive defensive preparations and the Mongol fleet sailed around for months trying to find a place to get ashore before the great typhoon finally wiped out most of the fleet. The Japanese executed any Mongols and Koreans and Northern Chinese who made it ashore, sparing only Southern Chinese, who the Japanese believed had been coerced by the Mongols; the Japanese made them slaves.
Some accounts claim Mongol losses at over , men. Ironically, had Operation Olympic gone forward with X-day on 1 November , it too would have been severely impacted by a typhoon. The Pacific typhoon season in was very active with 26 named storms, lasting from April into November. The first typhoon to hit after the Japanese surrender was Typhoon Ursula September during which six transport aircraft flying from Okinawa to Manila were lost; all recently liberated U.
However, in early October, Typhoon Louise took a sudden unexpected turn and on 9 October hit Okinawa full force, with hundreds of U. Twelve ships and craft were sunk, were grounded, and another 32 severely damaged beyond repair.
Casualties included 36 killed, 47 missing, and over with serious injuries. Three destroyer-minesweepers and a destroyer escort were driven aground. The destroyer escort, Oberender DE , was refloated, but the three destroyer-minesweepers were deemed not worth repair.
About amphibious craft were grounded, many of them wrecked beyond salvage, including four of six LSTs that were driven aground. Eighty percent of the buildings on Okinawa were destroyed or severely damaged, many still packed with war supplies. All 60 aircraft on Okinawa airfields were damaged.
Only a month earlier, hundreds of aircraft were crammed on Okinawa airfields as well as many more ships and amphibious craft. The toll would have been far higher had Operation Olympic been underway. Instead, the vast majority of ships and aircraft were gone.
Estimates shortly after the typhoon concluded that Operation Olympic would have been delayed by 45 days, which then would have put it in the teeth of winter storm season in planning for Olympic, 1 December had been assessed as the last feasible date for the operation. Japanese Terutsuki class destroyer in Moji harbor, Kyushu, 15 September Although the U. Japanese Intelligence correctly estimated that the main objective for the initial U.
Southern Kyushu was just within the maximum range of U. The Japanese also correctly assessed that the U. The Japanese also with uncanny precision predicted the exact beaches on Kyushu that would be the target of the first landings.
Although the Japanese initially thought the landings might occur as early as July, they changed their estimate based on the length of time it took the U. The Japanese accurately predicted that the landings would occur at the very end of October or the beginning of November.
As a result, the Japanese had ample time to reinforce Kyushu, which they did, going from one army division in the spring of to over 15 divisions by late summer. Of note, some of the low-end U. The Japanese assessed that the critical U.
Thus, the primary objective of Ketsugo was not to hold territory or destroy equipment, but to kill as many Americans as possible regardless of the cost to the Japanese. The objective was to break the will of the American people to sustain such high casualties so that the war could be ended with a negotiated settlement that did not lead to foreign occupation of Japan. It is also apparent from Japanese plans that they intended to throw everything they had at least in terms of aircraft and naval vessels into the defense of Kyushu with the intent to kill as many Americans as possible at the beachhead.
Thus, American troop transports and amphibious ships were identified as the primary targets. Although the Japanese did not have the means to get their entire army onto Kyushu for logistical and air threat reasons, the Japanese did not intend to hold back aircraft or naval vessels for the expected follow-on landings near Tokyo.
The specific plan for the defense of Kyushu was Ketsugo No. The defense of Kyushu was the responsibility of the 16th Area Army, made up of three armies with a total of 15 divisions, seven independent mixed brigades and independent tank brigades, and two coastal defense divisions. By the time of the Japanese surrender, this force had reached a strength of over , men. This exceeded the , men in 13 U.
The total U. The effects of U. The Japanese battle plans envisioned fighting in such close contact with U. During the course of the war, the Japanese had learned much the hard way. In a nutshell, these principles were:. The Japanese first line of defense against the invasion of Kyushu was what was left of the Imperial Japanese Navy, as aircraft were not expected to be committed until troop transports were in close proximity to the beachhead.
Of the 46 remaining Japanese submarines, about 38 were operational in Japanese waters and would be the first thing U. Although an opportunity to sink a carrier would not be passed up, the troop transports were top priority. A few of the Japanese submarines were equipped to carry Kaiten manned-suicide torpedoes and about Kaitens would be immediately available for use, although some estimates for the number of Kaitens that would have been available by November range as high as 1, Although the Kaitens had proved largely ineffective in open-ocean use, the Japanese anticipated much better success in confined and crowded waters of an amphibious beachhead, which probably would have been the case.
Japanese kanji character painted on the fairwater of Kaiten number 26 is yoko, probably a unit marking for Yokosuka naval base.
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