How long would operation downfall take

But the Japanese were clever as they knew that very few beaches could be used for landing. Both the sides also knew that for a big amphibious landing, only the beaches of Kyushu and Kanto near Tokyo are capable. Keeping this in mind, the Japanese took the appropriate measures in time. Because of all this, the invasion took more time to accomplish. Thus, it resulted in this amount of days for Operation Downfall.

A plan was made to land first on the beaches of Kyushu, and then attacked the other targets in Japan by using Kyushu beaches as the base of their planes. Then the plan afterward was by taking support of the same aircraft for landing on the beaches of Kanto to have complete domination upon the beaches of Japan and direct fires from there. The Japanese were too early to guess this plan of Americans landing on these beaches for a massive force of amphibious troops.

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. Top fin of the Kaiten in the foreground features a painted Japanese navy flag. Official U. Navy Photograph, now in the collections of the National Archives. The Japanese already had quite a few midget submarines, which had been held back thus far, and were building more. However, Koryu production was severely impacted by bombing and only were complete when the war ended, and only of the Kairyu had been completed.

The larger vessel in the drydock, right background, appears to be a barge. Flooding, deposit of debris including a bulldozer and other damage was done after mid-October Air Force photograph.

USAF K Once the American assault was underway, the Japanese navy would shift to phase two, expecting to commit all 19 of their surviving operational destroyers to one-way suicide attacks on the amphibious ships. The Japanese also intended to commit about 3, Shinyo suicide boats most army-manned and some navy-manned. The estimated numbers of Shinyo are very squishy, with some as high as 6, What is pretty firm is that by the end of the war Shinyo had been assigned to the 16th Area Army on Kyushu.

Equipped with diving suits and oxygen, the Fukuryu would swim to the surface with explosive charges to take out landing craft as they went overhead. Air operations in support to Ketsugo No. Post by Kingfish » 05 Jul It would have taken more than a few months. Downfall was divided in 2 parts - Operation Olympic was planned for November '45, and Coronet for March ' The gods do not deduct from a man's allotted span the hours spent in fishing.

Post by Kingfish » 05 Jul OpanaPointer wrote: Do they include the ten atomic bombs Marshall was to be given control of for used during the invasions? Post by OpanaPointer » 05 Jul Kingfish wrote: OpanaPointer wrote: Do they include the ten atomic bombs Marshall was to be given control of for used during the invasions? Post by Markus Becker » 07 Jul Not sure the operation would have gone down that way or at all. They could have gone straight there but that would have made it a navy operation, something Mac Arthur strongly and it seems successfully objected too.

However with mounting evidence of Kyushu being thougher than expected and Mac not giving in, the USA might have done what it planned to do since the start of the century. End a war with Japan by blockade and bombardment instead of invasion. Post by OpanaPointer » 11 Jul Markus Becker wrote: Not sure the operation would have gone down that way or at all.

Too expensive in men and material. The Japanese could have just squatted down and refused to surrender. Operation Downfall was the name given to the planned invasion of Japan. By mid- , it was apparent that the collapse of Japan was near and the Allies had to plan for the invasion of the Japanese mainland — something that they knew would be very costly in terms of lives lost.

Eventually the navy accepted that MacArthur was to have total control if the invasion was to take place. The planning proceeded without taking the atomic bomb into consideration as so few knew about its existence. The Americans faced one very serious problem. They knew for sure that the Japanese would defend their territory with zeal and that American casualties would be high — probably too high for the American public to accept.

The fanaticism that had been shown by the kamikazes , would almost certainly be encountered in Japan and the Americans had to plan for this. There was plenty of evidence to indicate that any invasion of the Japanese mainland would be very bloody for all concerned.

The complexity of such an attack also led to both sides of the US military developing different ideas as to what the best plan should be.