World War II in the Pacific
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Operation OLYMPIC, Nov 1, 1945, after the hurricane season, before winter. General Krueger, Sixth Army, with nine divisions (3 more in reserve) was to invade three beaches in southern Kyushu, the southern-most of the four Japanese home islands. This was to became a giant airbase to support the next invasion phase in the Spring of 1946. The Japanese had correctly predicted our invasion point and had reinforced Kyushu threefold over initial US expectations.
Operation CORONET, March 1, 1946, of Honshu, the main island, with 22 divisions in the Spring after air fields on Kyushu allowed landbased air support. There were to be two prongs:
General Hodges, with the 1st Army to land east of Tokyo, clear the peninsula, establish air fields, land tank divisions transferred from European, about 30 days, then charge across the plains to take the capital.
Ten days after the initial landing, LtGen Eichelberger with 8th Army was to attack west of Yokohama, Tokyo's seaport, open Tokyo Bay and block any reinforcement of Tokyo.
U.S. PREPARATIONS
The previous phase of the war had been the capture of the Marshalls --Saipan, Tinian and the US island of Guam during June, July and Aug 1944. These were captured to provide air fields within the effective range of B-29 Superfortress, very heavy bombers. Previous attempts to fly B-29's from inland China could only reach the southern portions of Japan with minimal bomb loads and required an impossible to maintain rate of logistics. B-29 attacks started in November 1944, by March 1945, Tokyo, Osaka and other industrial cities had been bombed.
Iwo Jima was taken in Feb-March 1945 to provide an intermediate airstrip for damaged B-29's, and for fighter escorts, and for shorter ranged B-24 Liberator heavy bombers. Air attack was ratcheted up to 300 plane raids and the attack method changed from explosives to incendiary in which 15% of Tokyo was destroyed in the first raid.1
Air dropped mining began in March 1945 in the Shimonoseki Straight, separating Kyushu and Honshu, to isolate the invasion island. Over 120 ships succumb to these mines.
Submarine efforts were concentrated in the Sea of Japan, on the northwest coast, while carrier task forces concentrated on the Pacific Ocean side.
Preparation for the invasion began with the Okinawa campaign. This is the largest island in the Ryukuyu Islands, the chain nearest to Japan. The native Okinawans were of Chinese extraction but had been an independent kingdom for 800 years until Japan invaded in 1875. Annexed, they continued a race apart, looked down upon my Japanese.2
Carrier Task Forces. The first strike on Japan's home islands was the period 18-22March 1945 to disrupt attacks on our invasion fleet as it approached Okinawa. Raids by 11 fleet carriers and 6 light carriers destroyed aircraft such that the Japanese air attacks on Okinawa were delayed until 6 days after the landings.
Remnants of the Imperial Navy were destroyed in their yards at Kure (near Hiroshima) on the main island of Honshu during early July.
Two fleets were to participate in Olympic: The Strike fleet with 21 carriers, 10 fast battleships and their train. The Assault fleet had 1,500 transports and 800 warships including 26 carriers and 13 battleships.
Operation Zipper by Lord Mountbatten's southeast Asia command was to take Singapore and the Malay Peninsula about 1Sept45. Also, the US China theater was planning to take the Liuchow Peninsula, west of Hong Kong, in mid-August as a port to supply China.
JAPANESE DEFENSES
Troops. Japan was scrapping the bottom of a big barrel. Two million new recruits were called up and experienced Armies was brought back from China and Manchuria to defend the homeland.
Kamikaze. Numbers of about 2000 Navy and 3500 Army airplanes have been cited as available for the defense, and of course, preparations would have continued with 500 mini-subs under construction, specially designed aircraft build, motor boat and manned torpedo stations established. Japanese military was committed to and was convinced they could repel the initial assault. That we might make as second assault was too much to consider. 1,465 Kamikaze had attacked at Okinawa, 400 miles away, had sunk or damaged 250 warships. A ratio of 1 hit per 6 attempts. Troopships sailing into waters adjacent to Japan, they thought, didn't stand a chance. US planners estimated 250 hits; Japanese planners expected 480 ships sunk. See suicide page for a range of special attack (suicide) weapons used by the Japanese.
Expected casualties. By this stage in the war, the overwhelming American material condition had reduced the ratio of American killed vs. enemy. The assault by Pacific trained Army troops from the Philippine Campaign and combat hardened Marines lessened the expected causalities on the American side. Conversely, first rate Japanese troops with pre-war combat experience in China -- which had made the initial conquests in the Pacific against inexperienced Allied troops -- had mostly been killed. The combat trained troops in China had been replaced with secondary troops -- these now experienced troops were recalled to defend the home islands. These troops had never been exposed in China to the massive air attacks that were now normal operations from US land and sea forces. Japan's naval ships had been destroyed. Japan had never had an adequate new pilot training program. Industrial resupply was dramatically weakened with every war facility destroyed as soon as it was discover by American air reconnaissance. Raw materials had been cut off as the merchant marine was destroyed by American submarines and aircraft.
Usually omitted from the statistics, however, because the atomic bomb was a secret, is the 300,000 white slave laborers held by Japan. Most of these were to be executed if the invasion had happened. The appearance of the atomic bomb brought such a sudden end to the war, that these lives were saved, along with the expected military casualties of both sides and massive numbers of Japanese civilian population either participating in the defense or as collateral damage.
Prospects of Operation Olympic. Japan fully expected to be able to repel the first landing with the help of suicide tactics. As shown at Normandy, the Americans expected to overpower all in their way. The U.S. expected to have air superiority, which places an imposition on the defense. The Navy expected to interdict all movements of resupply and reinforcement.
Best guess, the attack would be a repeat of "bloody Omaha beach" with a successful American landing. The plan called for sealing the mountains rather than fighting an Okinawa type campaign. The goal of establishing air bases would proceed as an American specialty. There would be continued casualties, but the goal accomplished.
CORONET . With American aircraft numbers measured in the 5-digits by aircraft type, and Japan's total aircraft numbers measured in the 4-digits, possibly 3-or 2-digits after Olympic, it is inconceivable why Coronet should happen. Japan could be allowed to suffocate under a siege with sea and air attack. No item of military importance would exist within 10 miles of the shore or any item that could be seen from the air. However, if Japan had persisted, it could only be because of great resistance at Kyushu. The momentum of war would have followed the plan. Invasion of the main island of Honshu would have been brutal with total destruction of every square yard before the troops and ruthless combat. The atomic bomb not only saved many Japanese lives, it may have saved the nation. With surrender, the occupying troops could be magnanimous in the American manner. If they had to fight fanatical resistance, they would have been compelled to destroy everything in sight as a potential military threat.
More. See the expansion of this page.
(1.) Photos of the devastation from fire bombing in Germany and Japan exceed that of like photos taken at Hiroshima and Nagasaki. The difference is that only one plane was required, rather than 500+ airplane raids which were being conducted by May 1945. A successful public relations program somehow makes the atomic weapon and its effect different than that of TNT, shrapnel, phosphorous or napalm. They all wreak havoc on the human body and on structures as is characteristic of warfare.
(2.) In the surrender, Japan lost the Ryukus and all colonies and conquests and retained only the home islands and "such as granted by the Allied powers." Today, when you hear that the U.S. has X-many troops stationed in Japan, they are really on Okinawa. Agitation to reduce the American presence is just that, agitation. The islands are not of the islands known as Japan, they were a Japanese colony and were freed by force of arms and were formally surrendered by Japan, confirmed in 1951 Peace Treaty. They are governed by Japan again, since 1972, by the graciousness of the United States with treaty commitments to station troops there -- rather than on the main islands.
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About this page: downfal0 - Overview of Operation Downfall: the planned invasion of Japan. Last updated on August 22, 2002
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