Military History: Invasion Japan

By: Jim 'Twitch' Tittle
Date: 2005-08-09


Richard Gibney's Landing on Tarawa

With the 60th anniversary of nuclear warfare upon us I wonder if anyone still thinks that it would have been better for all if we had invaded Japan proper? Many theorize alternate scenarios of paths that should have been taken. After island hopping the Pacific would our momentum have carried us to Tokyo on the ground?

I found a few calculations and projections of casualties that are beyond the usual stale historical rhetoric. And there were some wildcard factors that would have modified any educated predictions of intelligence of the day. Most of the eyebrow raising findings post war that would have been spoilers of educated guesses got little or no publicity at the time. Once the war was over the public simply wanted to be rid of news about the conflict and move on.

In four parts we will examine both known and obscure data on war planning and hardware to see if there’s anything we missed so long ago.

On August 2, 1939 Albert Einstein was prompted by fellow physicists Leo Szilard and Enrico Fermi to write President Franklin Roosevelt expressing their concern over German activity in nuclear physics. Why? Because German scientists, Otto Hahn and Friedrich Strassman, had split the atom in December 1938, and Germany was known to be stockpiling uranium. Only a few scientists in the world understood the seriousness of what that indicated. The decision to have Einstein write to the President was because Szilard‘s earlier attempts to alert the government had failed, and it was expected that such a letter from Einstein would draw serious attention given his stature.

Upon learning of this German experimentation into nuclear weaponry, the U.S. did begin work on the A-bomb in 1940 under the code name “Manhattan Project”. While “the rest is history” concerning the first atomic bomb successfully tested on July 16, 1945 in the desert outside Alamogordo, New Mexico, there have always been “what if” conjecturers regarding the decisions that led to Hiroshima and Nagasaki. There are some new things to consider concerning the decision to use the atomic bomb instead of invading that I have not seen factored into before that should be pondered.

President Franklin D. Roosevelt authorized the Manhattan Project. He died April 12, 1945 and Harry S. Truman became President. Incredibly, at the time he became President, Truman had never even been briefed on the A-bomb and had no prior knowledge of it even as Vice-President. Yet it would be Truman who would ultimately make the decision to use the weapon. Germany surrendered May 8, 1945, but we were still at war with Japan until August 14, 1945. The official reason for dropping the bomb was to shorten the war and save lives, both American and Japanese.

The summary conclusions of the 1945 Intelligence Report on the proposed invasion of Japan (Operation Downfall) was as follows:

  1. Japan would not surrender unconditionally without a demonstration of total destruction.
  2. In an invasion of the Japanese home islands, the people would fight to the death to protect their nation.
  3. An invasion of the Japanese home islands would cost approximately 1 million American casualties and perhaps 10 million Japanese.

Our experience fighting the Japanese in the Pacific tended to support these predictions. As the “island hopping” strategy neared the Japanese home islands, Japanese resolve to the war stiffened. There was an estimated 3000-5000 kamikaze attacks during the battle of Okinawa alone, and 36 ships were sunk with 368 damaged by this tactic.

The reluctance of Japanese soldiers to surrender in the island battles, fighting to the death or committing suicide, was further evidence. On Saipan there were mass suicides after the fighting committed by the civilian Japanese population. On Iwo Jima, fewer than 30 out of the 22,000 Japanese troops defending the island surrendered and only about 200 had been captured. The U.S. death toll was over 7,000 and total U.S. casualties, killed and wounded, for Iwo Jima was over 28,000. On Okinawa, the U.S. suffered over 12,000 dead of 49,000 casualties while Japanese and Okinawan combatant dead alone was 107,000. Another estimated 20,000 were incinerated with napalm and flame throwers where they holed up. Civilian deaths were in the order of another 100,000 out of the island’s 450,000 inhabitants. 40% of the Americans killed were the result of kamikaze attacks. 20%- 5,000- of all US Navy casualties endured in the war were suffered at Okinawa.

These battles were significant in estimating the level of resistance and the possible casualties to be expected in an invasion of the Japanese home islands. They illustrated that as the fighting drew closer to the Japanese homeland casualties on both sides grew and combat was more desperate and protracted in scope.

Operation Olympic dealt with the Kyushu island invasion. The main island scenario was called Operation Coronet.

A committee that examined the possibilities for the use of the bomb came up with four possible courses of action that the President could take to end World War II.

  1. Do not use the bomb. Blockade Japan by sea and air cutting it off from all outside supplies. Invade using conventional warfare.
  2. Demonstrate the power of the bomb on an uninhabited site. Invite a delegation from Japan to view the demonstration so that they might relay information about the bomb’s power and destruction to the high-ranking officials in the Japanese government. Such information would encourage the Japanese government to submit to the demand for unconditional surrender.
  3. Use the bomb on a Japanese city with military significance after announcing the intended target. The warning would allow the evacuation of the city by its inhabitants.
  4. Use the bomb as a weapon of war on a city with military significance and without prior warning.

At the same time, a list of cities was drawn up as possible targets. The selections were based on the criteria that the city had military significance from its factories, harbor or other facilities, and that the city that had suffered little prior bombing in order to demonstrate the maximum effect of the atomic bomb. The final list of four cities included Hiroshima and Nagasaki. The committee offered further comments on each of the options for the President:

  1. An invasion would be incredibly costly in terms of lives to both the U.S. and Japan. It would easily be the most deadly action of the entire war for the United States. However, the Navy maintained that a blockade would eventually bring surrender without an invasion.
  2. No demonstration was certain. Such a demonstration might fail and give the Japanese a morale boost. Also, only three bombs had been completed. One had been tested in the New Mexico desert. If a demonstration was held and the Japanese did not surrender, only one bomb remained to be used as a weapon of war.
  3. A preliminary announcement might bring a movement of prisoners of war into the area by the Japanese government.

Faced with these predictions and recommendations, Truman made the decision to use the weapon.

There are other interpretations of our decision to use the bomb. Some say that decision was precipitated more by our deteriorating relations with the Soviets than by our concerns for casualties, and that the decision was one of the early steps in the Cold War.

At the time of the atomic bomb test, Truman, Churchill and Stalin were at the "Big-3" Conference at Potsdam, Germany. This was Truman's first direct meeting with Stalin and already he had become suspicious of Soviet motives. At the Yalta Conference in February 1945, Stalin's promise of aid in the war against Japan had been sought and secured. He agreed that after the defeat of Germany, the Soviets would enter the war against Japan in exchange for Asian territory: the Kurile Islands and southern Sakhalin Island. We agreed to these cessions at the time because of the predicted high cost in casualties of a Japanese invasion and the estimate that the war in the Pacific might last into 1947.

By August 1945 we no longer needed Soviet help because of the existence of the A-bomb. Also we no longer trusted Stalin and wanted to prevent Soviet troops from invading Japan. The Soviets had already shown their reluctance to withdraw from "liberated" territories in Europe. It made no sense to offer more opportunities for expansion in Asia. Stalin simply wanted a piece of the action, equaling Japanese territory. The US and Britain simply did not want a carved up and divided post-war Japan. Using the bomb to end the war quickly would prevent Soviet entry and occupation of Japan.

It was during the Potsdam Conference of July-August, 1945, that the bomb was successfully tested. The U.S. didn’t share this information with Stalin, which some claim added to Stalin's distrust of the U.S., placing blame on the U.S. for initiating, or at least contributing to the coming cold war. We did, however, announce that we had a "super weapon" and the 3 powers issued the Potsdam Ultimatum warning Japan to surrender unconditionally or face utter destruction. No mention was made in the ultimatum of the nature of that destruction. Japan refused, of course. The first bomb was dropped on Hiroshima, August 6, 1945. American estimates claimed 80,000 dead and Japanese estimates claimed 200,000 dead. On August 8, the Soviets declared war on Japan and attacked Japanese forces in Manchuria. On August 9, the second bomb was dropped on Nagasaki, destroying one third of the city. August 14, Japan agreed, though reluctantly, to surrender. Surrender papers were formally signed on September 2, 1945.

Arguments and counter arguments concerning the use of the bomb, especially the second bombing, have been flying ever since. The summary stated:

  1. The official argument in favor of dropping the bomb was that it shortened the war and saved lives- American and Japanese. More casualties were inflicted by the fire bombings of Tokyo than in either of the atomic blasts. Officials also pointed out that both targets were military-industrial targets important to Japan's war effort.
  2. Opponents of our decision argue that we should have given Japan a clearer warning about the nature of the bomb, perhaps staging a demonstration on some uninhabited island. This may have brought surrender without use against the Japanese population. Proponents of the bomb counter this charge by arguing that
    A) we didn't want the Soviets to know the nature of the bomb, therefore we couldn't tell the Japanese;
    B) we couldn't demonstrate the weapon for a number of already stated reasons such as what if the demo was a dud? What if the Japanese moved U.S. POWs into the test area? We only had two bombs and couldn't waste one on a demonstration.
  3. Opponents also argue that Japan was on the verge of surrender and indeed had asked the Soviets to approach us for terms of surrender. If true, this argument is countered by several points. Firstly, the Soviets never passed those peace feelers along to us. They had a vested interest in keeping the war going so they could enter and claim their spoils. Also, at the time the first bomb was dropped, the Japanese War Council was divided and deadlocked 3 3 on the issue of surrender. Even after the first attack, the Council remained deadlocked. It required the intervention of the Emperor after the second bomb to break that deadlock. This evidence does not suggest that Japan was on the verge of surrender.
  4. Opponents argue that had we not insisted on unconditional surrender, Japan may have been willing to surrender. The main reservation they wanted was a guarantee of safety for the Emperor. Since we had no intentions of executing Hirohito, it would have been an easy condition to agree to, yet we refused. There never was any power given to the idea that Germany was to have conditional surrender either and Japan’s pre-emptive strike on Pearl Harbor and atrocities against Allied servicemen made it a moot point.
  5. Perhaps the strongest argument of the opponents is against the hasty dropping of the second bomb. The Japanese sent a team to investigate the destruction at Hiroshima, but given the extent of the destruction and damage to communications, it is argued that they really did not know immediately what they were facing. If more time had elapsed between the bombings and they had time to analyze the Hiroshima incident, perhaps they would have surrendered without the second bombing. The Soviet declaration of war on August 8th made the immediate conclusion of the war a priority which led to the Nagasaki decision.
  6. Some have argued that the bombs dropped on Japan were used just as much as a demonstration of U.S. power to the Soviet Union as they were to end the war. At the Yalta Conference in February 1945, the Soviet Union had promised to enter the Pacific war against Japan within 90 days of the end of the European war. The progress of the Manhattan Project in developing the bomb meant that conventional Soviet participation was no longer required. Soviet behavior in occupying Eastern Europe was raising suspicions about their post-war goals also. If the war could be terminated before the Soviets entered the Pacific war, they could not argue for any territorial gains in Asia. The bomb would be the ultimate demonstration of U.S. military power and a threat to anyone that might challenge it. Stalin declared war on Japan on August 8, 1945, which was exactly three months after V-E Day, 2 days after the Hiroshima bomb and 1 day before Nagasaki. At any rate, Japan surrendered unconditionally on August 15.

The large contingent of Japanese troops in Manchuria, nearly 3 million strong, was another factor in favor of the bomb. They were in relative terms fresh having been left guarding the back door to Japan, as it was. They were a counter measure against the Soviets coming across the border but it was feared that if these troops were to return to Japan and bolster the ranks it would embolden the Japanese war machine and strengthen its defense.

After the hostilities it was discovered that some 12,000 combat aircraft existed, which were the products of underground factories that the Allies were completely unaware of. This was a real shocker since many would have been kamikazes.

All of the estimates of 250,000 Kyushu-1 million main island, Honshu, Allied casualties would have increased since the 12,000 hidden, unknown planes were never factored into casualty estimates as it was. And to start with, theses estimates were conservative.
An additional factor is that if conventional conflict had drawn out to 1946-47 as it was estimated, the unknown Japanese underground factories would have made more jets, many more conventional planes and several types of rocket-powered craft that were in development for kamikaze use. A Spring of 1946 invasion date would have allowed plenty of extra time for untold numbers of aircraft and troops to be added to the Japanese side of the equation.

The Joint Chiefs of Staff April 1945 estimates implied that a 90-day Olympic campaign would cost 456,000 casualties, including 109,000 dead or missing. If Coronet took another 90 days, the combined cost would be 1,200,000 casualties, with 267,000 fatalities. Since no one knew of the secret manufacture ability, thousands of planes and other sea-borne kamikazes were never considered or projected into calculations so the casualty number certainly would have inflated if they had.

The first 48 days at Normandy resulted in just 63,000 casualties and we owned the air and sea! Luftwaffe ace Josef “Pips” Priller and his wingman were the only two aircraft to appear over the Normandy beaches. Such would not have been the case over and around Kyushu.

Inside and outside the government sources studies concluded 1.7- 4 million American casualties, including 400,000–800,000 fatalities, and 5 to 10 million Japanese fatalities assuming a large-scale participation by civilians in the defense of Japan.

As it was in reality the US suffered about a million casualties with some 300,000 fatalities during the entire war.


Richard Gibney's Landing on Tarawa

Some more points to ponder and a look at anti-invasion hardware.

Ok so let’s say when the decision was nuke or not nuke Japan we refrained from the atomic bomb’s use and invaded. What would we have met if that were the case?

Why do we speak of a Spring 1946 initial invasion when November 1, 1945 was the tentative invasion date of Kyushu? One little-known factor that is never discussed is the fact that the worst typhoon in US Naval history swept the proposed armada assembly area off Okinawa on October 9, 1945. 403 ships were either sunk, destroyed beyond repair or scrapped. Countless aircraft were ripped to pieces in the 150 MPH winds along with hangars, other buildings and tents housing 150,000 troops. Harbor facilities were ruined, power was out and supplies blown away.

In relative terms, as it was, there was sparse damage considering a depleted American presence due to the fact that the war was over and personnel were greatly reduced. Had Typhoon Louise set upon the 22 divisions of more than half a million invasion-ready personnel along with some estimated 5,000 ships and 4,000 aircraft, the devastation would certainly been worse and would have no doubt delayed the November 1st date to invade Kyushu. It possibly would have been pushed back at least to the March 1946 date that was proposed for the Honshu invasion, which itself may have tentatively been strung out to summer of 1946 or later depending how the Kyushu fight went.

So before we would have moved one yard toward Japan our forces would have suffered a catastrophe of major proportion. In fact, since the battle for Okinawa had lasted so long it would have been highly optimistic to imagine operations of any sort during typhoon season which generally runs from June through November. A typhoon season attempted assault was lunacy at any rate considering a relatively mild weather front had postponed D-Day.

Olympic and Coronet proposed ultimately putting 5 million Americans at arms to subdue Japan in a final stranglehold of submission.

"Would it not be wondrous for this whole nation to be destroyed like a beautiful flower?" This from the Japanese War Minister, General Korechiki Anami, explains in part the Nipponese attitude even late in the war. “Fight to the death…” and “surrender would be treason…” were phrases in use at the time.

The estimate for Japanese troops to be on Kyushu in November was 350,000. As it was by May 246,000 were there and 300,000 by mid-June 1945. American KIA-killed in action were calculated from a low of 25,000 if the Japanese were to surrender, to 46,000 if they did not. 766,700 Americans were to be involved in Operation Olympic. General MacArthur argued that previous estimates of Japanese strength had always been optimistic anyway.

The actual number of Japanese on Kyushu by August 2, 1945- 534,000 was far greater than our intelligence estimates of 250,000! How many more would have poured onto the island and how well equipped and dug in would they have been after the US forces were postponed from their attack due to the typhoon? The true number of men assigned to defend this southern-most island of Japan was actually 900,000! They had 40% of all of the homeland’s ammunition. During the island hopping campaigns of the war the Americans always outnumbered the Japanese. Now the odds would be 3 to 2 in favor of Japan. There were a total of 2,350,000 men at arms in Japan in August 1945 and 3 million on the Asian continent.

The estimate of airworthy Japanese combat planes was 2,000 when in fact it was six times as many by mid-August with more, including jet and rocket powered craft, coming from underground factories. It is with little imagination that we can figure a lot more of all types would have been in service by March 1946 if the invasion force had recovered and rebuilt after Typhoon Louise by then. At any rate, they would have been complete surprises not accounted for in US casualty projections.

Operation Coronet’s estimates of US invasion troops was double that of Olympic’s if Kyushu was secured as was optimistically projected. Whenever in 1946 it would have taken place we can be assured that Japanese numerical superiority would have factored heavily. As it was, Coronet had very little in the way of concrete planning as though a wait-and-see attitude about Kyushu would prevail.

The fanatical Japanese will to win or die trying carried over to the civilian population’s National Volunteer Combat Force which consisted of 28 million! Boys as young as fifteen and men as old as sixty, as well as girls of seventeen and women of forty years of age were members. They were armed with outdated firearms, satchel charges, mines, Molotov cocktails, bows and axes right down to sharpened bamboo spears. Wouldn’t anyone fight for their own soil?

Beginning on Kyushu’s 35 landing beaches, all named for automobiles, and all along the road to Tokyo we would have seen a composite of the land mines, caves, pill boxes, mortars, barbed wire, snipers, suiciders in spider holes and the probable use of gas and biological toxic agents developed in China’s infamous Units 516 and 731. That was another little secret the West had little or no reliable intell about so no casualty scenarios including bio/chemical-warfare were conceived. It was dismissed that due to the dwindling air force no bio/chemical attacks could be launched.

Bubonic plague, cholera, smallpox, botulism, anthrax were propagated at Unit 731 along a variety of poison gasses from Unit 516. It is a certainty that there would be a wealth of volunteers willing to strap on ceramic canisters and charge headlong into the enemy.

The Imperial Navy still had 40 submarines, 23 destroyers and a couple cruisers plus innumerable kaiten suicide mini-subs plus thousands of small, fast explosive-laden kamikaze motor boats.

Artillery emplacements were to be supplied by stockpiles of shells from underground bunkers. Twenty airstrips with underground hangers would launch aircraft from Kyushu.

The Japanese Chief of the Naval General Staff estimates at first conceded that 60-70% of the attackers would make it ashore. Reassessing with more realism they calculated as many as 50% of the enemy would be vanquished before landing.

We can certainly see that the 250,000- 1 million casualties for the entire assault on Japan were dreadfully low.

Of course while the Americans would be slogging in coming from the south Russians would have been thrusting through Hokkaido and into Tokyo from the north and Japan would be a divided country like Korea or Germany.

Now we must realize that most likely the first offensive invasion action against Japan would have been postponed to spring of 1946 after regrouping from Typhoon Louise. Given this additional time to prepare and manufacture here is some of the hardware that would have shown up in Ketsu-go, the name of the defensive operation.

Unlike the Germans, the Japanese did not get into rocket development early on. When they did, around 1943, it was mainly focused on air-to-surface (ASM) anti-shipping missiles and surface-to-air (SAM). The Army never had multiple-projectile surface-to-surface ballistic rockets like the rest of the combatants in WW II, only single shot affairs that were dubious in effectiveness. The Navy Arsenal had a couple of potent SAM missiles called the Funryu (Raging Dragon). This was a Mitsubishi product. Four versions arose. The Funryu 1 was a radio-controlled ASM for anti-shipping use but it was stopped before much work was undertaken.

The 815 lb. Funryu 2 was a SAM with a gyrostabilizer powered by a solid fuel rocket of 5,300 lbs. thrust. Burn time was 3.5 seconds for the 7-footer to reach 525 MPH. The warhead contained 110 lbs. of explosives. Funryu 3 differed only on the substitution of the solid fuel rocket engine with a liquid-fueled one.

Funryu 2 left; Funryu 4 right.

The Funryu 4 was the most advanced and was to be the production model for use with AA units. It had a large 441-pound warhead moved along by a Toko Ro.2 bi-fuel rocket engine of 3,307 lbs. thrust. It was 13 feet long and about two feet in diameter weighing 4,200 lbs. A primitive computer was used to give telemetry info and course data to guide the missile to its target as it traveled at 685 MPH and as high as 49,211 feet. That guidance came from two radar stations- one tracking the missile and the other tracking the target. Range was 19 miles. The prototype of the Funryu 4 was ready for production when the war ended in August.

The straight-winged Igo ASM originated at Mitsubishi also. Three models evolved, the Igo-1-A, B & C. They were heavyweight ordnance able to be borne by only larger aircraft. The 1-A had a 1,764 lb. warhead- the same weight as a whole aerial torpedo- and weighed 3,086 lbs. It was 18.9 feet in length and had an 11.75-foot wingspan and could go 342 MPH and was radio-controlled. A solid-fuel rocket engine gave 529 lbs. thrust with a 75 second burn. Accurate range was about eight miles launched from 5,000 feet.

The Igo-1-B was scaled down considerably with 13.5-foot length and a span of 8.5 feet weighing 1,500 lbs. with a 661 lb. warhead. The incoming missile self-leveled at 100-500 feet altitude three miles out from the target. Guidance was by keen eye distance and depth perception alone since no optics were available for the weapons man. Tests proved it was excessive difficult to hit a target this way.

Testing of the 1-C began in March 1945. It was 11.5 feet long with all other specifications unknown except that it was to use an acoustical homing guidance system in place of the hit-and-mostly-miss human aimer.

A heat seeking bomb project to use in anti-shipping was commenced too late to show any results either but with more time who is to know? It measured 17. 9 feet long, was 19.7 inches in diameter, and weighed 1,764 lbs. with warheads of 441 lbs. to 662 lbs. weight.

It didn’t dawn on Japan to cultivate even unguided air-to-air missiles (AAM) or light air-to-ground rockets until spring of 1944. The Imperial Navy beat the Army in such development. Gestation, again, was excessive and the Shidens slated to use air-to-ground rockets on an invasion fleet never received them and the horde of Zeros scheduled to get AAMs never saw those either. With eight additional months would they have gotten into service?

Rocketry was a good way to get a lot of bang for the buck and they certainly would have been used as an invasion countermeasure.


Mitsubishi’s J8M1 Shusui (Rigorous Sword) was constructed using only the German instructional manual for the Me 163 since a submarine carrying a complete Me 163 to Japan was sunk. Gliders preceded a powered version. The J8M1 was a joint J.N.A.F.-J.A.A.F development project. Mitsubishi and the Yokosuka Naval Aeronautical Engineering Arsenal adapted the German HWK 109-509 rocket motor as the Toku Ro.2 with 3,300 lbs. of thrust. The Army’s designation was to be Rikugan (army) Ki-200 Shusui while the Navy would call it the J8M1 Shusui.


The type would have attained 559 MPH at 32,810 feet. It could climb to ceiling 39,370 ft in 3.8 minutes and to 19, 685 feet in only 2.25 minutes. With its 5.5-minute power endurance it would then seek targets using power as needed to intercept and by diving. It weighed 8,598 lbs. loaded and the wing spanned 31.1 feet while length was 19.1 feet. It was armed with two 30 mm Type 5 cannon with 60 RPG. By August 1945 seven were built and two flew. By March 1946 this one would have been flying in some numbers.

The Army devised modifications to their perceived needs and began development of what would become the Ki-202 Shusui-Kai, kai meaning modified. It would have a Toku-Ro.3-Go bi-fuel rocket motor 4,000 lbs. of thrust and weight would be 11,234 lbs. loaded. Wingspan was 32 feet and length was 23.3 feet. The same climb rate and level speed of 559 MPH at 32,810 feet was cautiously perceived equal. The difference in the other motor would mean burn duration of 10.5 minutes. It was pretty similar in all specs to the 11,280-lb. Me 163C which had a 52,000 foot ceiling over the 163B’s 39,000 feet. No Ki-202s progressed past design stages but certainly could have easily.

Here’s a plane that was intended for only one thing- kamikaze attacks against an Allied invasion force. The Shinryu, meaning Divine Dragon was originally a glider but plans to power it with short duration rockets were visualized. As a glider it could be towed by any aircraft to the intended target area whereupon it could dive down and crash into the victim. Why use engines when the same result could be accomplished without it?
But the later version with rocket power could have possibly taken off with a trolley like the Me 163 for short-range missions. Landing skids are illustrated in some drawings but it is unknown whether they were shown for glider training use or actual planned reuse of the craft.


At any rate the rocket’s burn duration would have meant that it had to be used when enemy targets were very close at hand if it were to take off from the ground since the Two Tokuro-1 Type2 rocket engines would have burned for 80 seconds only. What terminal velocity it would have achieved is unknown. Of course from a towed-to-altitude situation it could have stayed aloft a while with intermittent use of the rockets and gliding on the ample wings.

Another use of the Shinryu was as an anti-tank weapon. Taking off near enough the battle line the plane could get aloft and pick a target. Though a warhead with impact fuse could be installed, the pilot would have had eight unguided rockets if kamikaze was not the goal. Thusly the plane could be reused, at least in theory. A combination of rockets and warhead may have been imagined as a way to take out two armored targets- one with rockets and one by kamikaze.

No dimensional specs survive but the relative size of the modern-day illustration would translate out to about 30-foot wingspan similar to the Me 163 or J8M1 Shusui copy. There just is not much known about this craft or its supposed mission roles seemingly inspired by the J7W1 Shiden’s canard design.

Though fragile-looking it would have been a threat as a kamikaze if it was ground launched. In-flight towing is simply too dangerous all around to be effective.

The R2Y Keiun (Beautiful Cloud) was born from a specification by the Navy for high-speed, long-range reconnaissance from land-based airfields. The idea was that the plane would be immune to interception. As the war unfolded in the Pacific the Navy saw that the aircraft in service were not up to par anymore and, in 1942, they put forth specifications for a new aircraft. The only stipulation was that the aircraft must have a top speed of at least 414 MPH at 19,685 feet. The design of this new aircraft fell upon Dai-Ichi Kaigun Koku Gijitsusho of 1st. Naval Air Technical Arsenal at Yokosuka.
The design group planned to use the new Mitsubishi 24-cylinder, liquid-cooled “V” engine. The 2-seat plane was designated the Y-30 but known as the R1Y1 Seiun (Blue Cloud).

The engine development time would not meet the schedule goals for the new recon plane and a redesign of the Seiun was done. Now using two Mitsubishi MK10A radial engines, this new design resembled the P1Y1 Ginga bomber. Performance fell short of goals and the project was shelved.

New specifications came out so a nine man technical team, headed by Cdr. Hideo Tsukada, of the Yokosuka Arsenal went Marienehe, Germany to study and examine the promising He 119. They purchased manufacturing rights to the 119 and along with He119 V7 and V8, which were shipped to Japan in May 1940. Both were reassembled and flight-testing began. The R2Y1 was resurrected but need in 1944 for long-range recon was almost nil and the plane had to be re-thought as a heavy fighter.

It now had a tricycle landing gear and a scoop atop the aft fuselage to cool the Aichi 4,300 HP Ha.70-10 engine that was really two Atsuta 30s coupled. A drive shaft turned a six-blade prop. Wingspan for the 17,857-pound loaded plane was 46 feet and length was 42.75 feet. It took 10 minutes to attain 32,385 feet but at 32,810 it could do 447 MPH and had a ceiling of 38,385 feet. Range was 2,244 miles.

It finally flew in that form in early May 1945 but was soon destroyed in an air raid.

The Allies captured the second prototype in unfinished condition. How much fruitful reconnaissance it could have gathered is debatable but as a stepping stone to a pure jet design it was invaluable.

There was another version of the Keiun, the R2Y2. It was proposed as an attack bomber and, instead of being powered by the Aichi Ha.70-10s, it was to be jet powered. Where the Aichi engines were mounted would be fuel tanks for the 2,910 lb. thrust Ne-330 turbojets, which were to be installed, one under each wing ala Me 262. This concept was made in late 1944 and was the main reason the R2Y2 was of interest to the Navy. The speed of the R2Y2 was gauged at a 495 MPH maximum at 19.685 feet, making for a difficult intercept by Allied fighters. Even in recon configuration, for which it was originally designed, it would have proven tough to engage in missions into heavily defended areas.

R2Y2 With wingmount turbines

Span was 45.9 feet with length at 30.3 feet. It was to weigh 19,510 loaded with its 2-man crew. Getting to 32,810 feet took but 5 minutes and the ceiling was 34,448 feet. Range was to be 788 miles. Payload was either a 1,764 lb. torpedo or the equivalent in bombs. Probable armament would have been pairs of 20 mm and 30 mm cannon.
A proposed alternate engine mounting was to have had the jet engines paired side-by-side in the lower aft fuselage. The R2Y2 never made it out of the design stage but was slated to ultimately join the JNAF ranks for a Battle of Japan.


More hardware that would probably have seen combat in an invasion.

The Kikka (Mandarin Orange Blossom) was inspired by the disastrous defeat in the Marianas in June 1944. It was recognized that if the Japanese were ever going to be able to have any semblance of air superiority that was enjoyed by the Zero at the opening of the conflict, they would have to a radically new aircraft.

This plane was the “Nipponization” of the Me 262 and it was evident that many modifications had been done over the original.

The initial idea was to hang a pair of Tsu-11 engine that were copies of the Caproni’s of Italy. With but 441 lbs. thrust they were totally inadequate. However, Japanese R & D had produced a turbo jet designated the Ne-12 with 750 lbs. thrust. They failed to produce the stated power so the Japanese again got German assistance. An I-boat slipped under the Allied blockade with examples of the excellent BMW 003 turbines. It eludes logic why the Japanese didn’t simply clone the 003 bolt for bolt and have a fine engine but they made their own smaller version called the Ishikawajima-Harima Ne-20 with 1,047 lbs. thrust.

The Kikka

The Kikka could fly 422 MPH at 19,700 feet with a range of 345 miles. The ceiling was un-projected as was climb rate. The fighter weighed half that of the Me 262 empty at 5,070 lbs. and 7,826 lbs loaded. It span was less at 32.9 feet as was length at 30.25 feet. With wings folded it could get into a 17.5-foot cave or tunnel entrance. Two 30 mm cannons were the projected armament.

The Kikka actually had a decent power-to-weight ratio with 2,094 lbs. thrust in a crate weighing just 7,826 lbs. at 3.74 to 1. The Me 262 had 3,960 lb. thrust with the plane weighing 14,101 lbs. for a 3.56 to 1 ratio. Its span was 41 feet and length was 34.75 feet.

(It flew in August 1945)


200 Kikkas were ordered for delivery before the end of 1945 and twenty were in advanced assembly stages by August 15th. A two-seat trainer was on the drawing board. How many would have been flying by March 1946?

The Karyu or Fire Dragon was an extension of the J8N1 Kikka. But instead of a Nipponized interpretation of the Me 262, the Ki-201 would be much more of a straight copy whether with German sanction or not. Iwao Shibuya was the designer in charge of the project.

While the Japanese versions of the Me 163 rocket plane was developing as the Army’s preferred plane of 1946 production, the Navy demonstrated less interest in the Ki-201 though some production was scheduled.

The Ne-20 copy of the BMW 003 was a puny 1,047 lb thrust engine used on the Kikka giving just 422 MPH. The speedy development of axial flow turbojets with the Ne-230 at 1,951 lbs. thrust and the Ne-130 with 2,002 lb. thrust came to the rescue and a prototype was begun. The wingspan was to be 45 feet with length at 37.75 feet. The crate would weigh 9,920 lbs. empty and 15,432 lbs. fully loaded.

A pair of 20 mm Ho-5s and 30 mm Ho-105s were to fire from the nose. Maximum speed was calculated to be 529 MPH at 32,810 feet with a ceiling of 39,370 feet and a range of 608 miles. 13.25 minutes were needed to reach 32,810 feet in a climb.

Basic Me262 copy

Two prototypes were near completion in August 1945. With power equal to the Me 262 and size just a bit larger, though 1,000 lbs. heavier, the Ki-201’s estimated performance figures seem quite realistic for a maiden flight scheduled in December 1945. Production deliveries for both Navy and Army was to begin in March 1946 with a radar-equipped version speculated. Perhaps it would have been produced sooner but it would have been involved in a delayed Operation Coronet in summer 1946 or later, for sure.

Certainly only excellent pilots could have flown the Ki-201. How it would have faired against American aircraft is only a wild guess but we may look at the 262 in Germany and make some assumptions.

This was a proposed, straightforward conversion of the excellent twin-engine P1Y1 Ginga bomber, code named “Francis,” with turbojets. The 2,002-lb. thrust Ne-130 units would have made for decent performance it was reasoned and modifications to existing airframes would make for speedy completion of planes.

In the summer of 1944 a special craft was designed to meet the kamikaze requirements. The Naval Air Research and Development Center commenced the Marudai project. The result was the Oka 11 (Cherry Blossom) rocket powered piloted glide-bomb using a 2,645 lb. warhead with five fuses.

The little coffin measured 20 feet long with a 13.5-foot wingspan. The spartan cockpit had a compass, altimeter, airspeed indicator, rocket temp gauge, and inclinometer. A G4M “Betty” was enlisted to tote the craft to within 25-50 miles of target, depending on altitude before launch. The three Type 4 MK 1 Model 20 solid fuel rockets propelled the tiny plane to high speed whereupon the pilot would nose over, choose a target and make a run in at over 600 MPH. Once away from the mother ship the Oka was impossible to stop. It was dubbed “baka” meaning fool in Japanese.

The Oka group was named Jinrai Butai (Divine Thunder). Its first operation on March 21, 1945 off Okinawa showed how strong the F6F Hellcat screens were. All sixteen Bettys and Okas were destroyed despite thirty Zero escorts.

During the savage struggle on April 16, 1945 seventy-four Okas were airborne under the Bettys. Fifty-six were dropped early or shot down while attached. Some Okas did find their targets but exactly how many and other details remain uncertain. The destroyer USS Abele was definitely sunk by an Oka.

An OKA 11 and a Baika

The Oka 22 had a jet engine that would allow release from seventy miles distance and a 630 MPH dive speed but was not implemented by war’s end. The Oka 33 had yet a better jet engine, the NE-20 of 1,047 lbs. thrust but were too heavy to be carried by Betty or Ginga-“Francis” bombers. The four-engine G8N- “Rita” was to have been the carrier but production of the G8N was miniscule and the Oka 33 was abandoned in favor of the Oka 43 that was to be ground catapult launched against invading Navy ships if the war would have continued with an invasion of Japan. The final machine of this type was the Kawanishi Baika (Plum Blossom) with a Maru-ka Model 10 pulsejet engine like the V-1. This would have had great range and all would have impeded an amphibious invasion force.

Like advanced German projects these were all begun too late in the war when resources dwindled and Allied might was too powerful for them to have made any significant difference in the outcome. Deployed earlier in greater numbers or employed in a protracted war, they would have been unstoppable once launched. I would expect that a ground launch rail like the V-1’s would have been used by the time of invasion since lumber Betty mother ships would have been useless death.


As if all the proceeding technology weren’t enough, the other special operation weapon the Japanese used from the morning December 7th was the midget submarine. From 1934 to 1944, the Japanese Navy constructed many midget submarines. They were carried by larger Japanese submarines and other ships. Midgets were used for special operations against ships in enemy harbors, like the Pearl Harbor attack. In May 1942 raids on Sydney, Australia, and Diego Suarez in the Indian Ocean were carried out. The diminutive boats also were used off Guadalcanal in 1942-43, where they achieved some modest success against U.S. shipping. They were employed as shore-based defensive units in the Aleutians and elsewhere in the Pacific Theater.

Type A midgets displaced 46 tons, were 78 feet long and carried two 17.7-inch diameter torpedoes. They were propelled by electric motors and were capable of some 20 knots but range was limited. Type B and production Type C boats were fitted with a diesel engine to recharge their electric batteries. They resembled the Type A, had a second crew member and were longer and heavier.

Approximately sixty production Type A midget submarines were built between 1934 and 1942, and used designation names in the "Ha" series (Ha-1 through Ha-52 and Ha-54 probably through Ha-61). The lone Type B was Ha-53, then fifteen Type Cs (Ha-62 through Ha-76) were built in 1943-44. Ha 19 was made famous when the midget was captured on December 7th, 1941.

By mid-1944 the tide had turned and coastal defense requirements become a priority. The Japanese Navy developed an improved version of the A, B and C Types designated "Type D" and nicknamed Koryu, the new layout was larger than the earlier types. They had more powerful diesel engines and had significantly longer ranges. The Koryu also had a five-man crew, two more than in the Type C, but had the same armament of two 17.7-inch torpedoes.

The Type Ds displaced 60 tons and were 86 feet long. Propulsion came from a 500 HP electric motor giving a maximum speed submerged of 16 knots. Surface power was provided by a 150 HP diesel that charged the electric batteries. Speed was 8 knots and range some 1000 nautical miles. Each boat had names in the "Ha" series.

The first Type D boat was Ha-77, was completed in January 1945. 115 units had been built when Japan capitulated in August 1945.

Some of these subs were to be trainers for kaiten type manned torpedoes had larger conning towers and had two periscopes. Time in any of the mini-subs or kaitens was not pleasant. They were cramped, cold, stale-aired and battery fumes and propulsion chemicals could make the crews sick.

Minis ready to rumble

500 more were under construction. Though these subs existence was not known at the time, this was another good reason against Allied invasion.

In reality the midget subs were considered expendable even though mother ship submarine captains duly waited well past their probable time for rendezvous. Some did return after launching their torpedoes but most did not and the stoic crew expected to die in them.

By 1944 with aerial kamikaze operations going it was decided that kaitens (Turning of the Heavens) would be used underwater as well.

This weapon was based on the excellent Model 93 Long Lance torpedo with its oxygen-kerosene engine. The Type 1 was 48.24 feet long displaced 8.6 tons and used 2 Type 93 motors. Its single crewman could deliver its 3,300 lbs. of explosive at speeds as high as 30 knots for one hour and could maneuver for 78 miles at 12 knots.

The Type 2 used a single motor from the Type 6 torpedo in its 55.1-foot hull that displaced 18.4 tons. The crew of two could hit 40 knots and travel 83 miles at 20 knots to ram its 3,300 lbs. of explosives against a target.

Many submarines were modified to carry and launch three to six kaitens. The pilots entered the weapons while submerged through a connecting hatch. The ideal scenario would be for the mother sub to launch the weapons 7-8,000 meters from target. He would be on compass heading only and would risk use of the periscope only to acquire the target about 1-1,500 meters out.

The few successful contacts resulted in thunderous destruction but the vast majority of missions led to nothing at all. Kaitens must have missed entirely and ran out of power or were sunk by either enemy or mechanical failures. At any rate the successes did not justify the expenditure of lives. But given a ducks-in-a-barrel scenario of an Allied invasion fleet spanning the horizon, these things would have hit many targets.

Shinyo (sea quake) was the Japanese Navy name and Maru-ni (capacious boat), was what the Army called the motorboats laden with explosives for suicide runs against American shipping. 6,200 Navy and 3,000 Army boats were hidden in caves awaiting the invasion. They were one-man size carrying two depth charges for their destructive force. They were about 22 feet long with a 5-foot beam weighing 1.4 tons capable of 23 knots.


When even small boats were unsuitable there was the Fukuryu (frogman) a mined swimmer who would swim beneath a ship and detonate his explosives.

In keeping with the personal approach to kamikaze, the army planned the use of a device called the Nikaku human anti-tank mine. Crawling between the treads of a tank and going boom made for a “one man tank” by Japanese thinking.

All these devices and tactics were in use by Okinawa. They were conceived to inflict damage with a very low expense both in hardware cost and in Japanese life. It is conceivable that if a Japanese rocket could be somehow manned for better guidance there would have been volunteers to kamikaze it into a target.


The definitive defensive weapon and some conclusions.

Ok so lots of people have heard that the Germans were working on nuclear physics with the ultimate aim of creating an atomic bomb, right? The 1.8 billion dollar Manhattan Project to produce the A-bombs that effectively ended the war is well known. What about Japanese endeavors in nuclear bombs? You thought there were none? Think again.

The chief persona of the Japanese atomic program was Dr. Yoshio Nishina who was an intimate associate of Albert Einstein. Dr. Nishina foundeded his own Nishina Laboratory of the Institute for Physical and Chemical Research in 1931 to study high-energy physics. He built the first cyclotron in Japan in1936. It was a 26-incher. A 60-inch, 220 ton cyclotron was built in 1937. In 1938 Japan also purchased a cyclotron from the University of California, Berkeley. Cyclotrons were used to separate fissionable material from uranium.

Nishida understood the military potential of nuclear weapons, and figured that the Americans were working on a genzai bakudan (atomic bomb). Unlike his counterpart, Heissenberg in Germany, he wholeheartedly sought to solve the atomic riddle and produce a weapon. In 1939, President Roosevelt funded the first nuclear studies into fissionable weapons in the United States. This prompted the patriotic Dr. Nishina to match the U.S. research and development of a nuclear weapon. Lt. General Takeo Yasuda of the Japanese Army decided in October 1940, that such a weapons program was worthy of study and the Japanese atomic program commenced in July 1941 under the guidance of Dr. Nishina.

The well-know rivalry between the Japanese Army and Navy diluted strength of production projects as each insisted their own weapon was of paramount importance even if it was nearly identical to the other’s. They perpetually wasted manpower and resources duplicating efforts. So it was in atomic research.

A completely separate atomic program run by the Japanese Navy was in simultaneous study in 1942. The project was called “F-Go” and was headed by Professor Bunsaku Arakatsu, who studied under Albert Einstein. Arakatsu built his own cyclotron too.

The Navy’s plan wisely was to harness nuclear energy as an power source in order to reduce the dependence on petroleum. As the war unfolded not favoring Japan the idea of making a nuclear weapon became more promising. Initially it was assumed that an atomic weapon could not be developed during the limited span of time of the war.

A search for uranium throughout the empire commenced. The Japanese military took what Nishina had learned so far and expanded the program. The Navy payed large amounts for uranium on the Chinese black market. And we know about U-234’s unsuccessful attempt to transport uranium oxide to Japan from Germany. How far the Navy project progressed is a matter of conjecture but a member of the team was Hideki Yukawa, the first Japanese physicist to receive a Nobel Prize in 1949.

So where did uranium ore come from? The atomic programs' found a source of uranium ore in Korea. Dr. Nishina experimented with a number of methods for enriching the uranium and decided that the gaseous diffusion method was the most rewarding. Colonel Tatsusaburo Suzuki coordinated the effort for the Army and built five advanced gaseous diffusion separators based on the smaller one developed by Nishina. The fate of these separators is a mystery.

In 1938 Germany and Japan met to discuss the feasibility of the production of atomic weapons and atomic energy. Theories were explored but techinal data was not exchanged at that time. Japan later requested assistance from ally Germany but it is not known how much material Japan received. This is lost to history. All we know of for sure is the one shipment of uranium oxide that was intercepted on U-234 just after VE Day.

The program was moved from Nagoya to Konan, Korea (North Korea now) in 1943 due to increasing bombing attacks. Some 40,000 worked at the facility 25,000 of whom were engineers and scientists. The facility was partly underground. About 400 worked in the underground cave area on the most sensitive aspects of the bomb. A project director coordinated with six other reknown scientists each contributing but one phase and unaware of the others.

By August 10, 1945 the Hiroshima blast had taken place so the men assembling the bomb worked quickly. If an Allied invasion was imminent Japan would need the A-bomb to make toast of the forthcoming American invasion armada. Stalin declared war on Japan on August 8th and with enough reinforcements free from European combat Russians crossed the Manchurian border.

After midnight the device was trucked to the Konan harbor. It was loaded aboard a small vessel and final preparations were undertaken for the test. Presumably an anchorage in an inlet some twenty miles away was to be the unsuspecting and unwilling live target area. It was filled with mostly wooden fishing boats and ships with sails.

The boat with the device was robot controlled and it puttered towards the anchorage before dawn on August 12th. The vessel beached itself just as the sun’s first rays of the day hit the water. The genzai bakudan triggered and the observers wearing welding goggles gasped at the immediate intense burst of light rivaling the sun.

The fire flash was about 1,000 yards in diameter and from it a mushroom cloud boiled up to the stratosphere. The vaporized water obscured the anchored vessels but most of them were burning. When the epicenter cleared some ships previously seen were completely gone without trace. The area of destruction was approximately one square mile.

But it was all too late. The Russians were hours away and the equipment at the Konan facility was smashed and the underground entrances blown up. The scientists were unable to escape and at least the top men were spirited away to Moscow for torture. The Soviets closed up the area quickly and tightly. American War Reparations personnel later were kept under constant supervision and restricted from many areas. Even a B-29 with humanitarian supplies was shot down by the itchy Russians.

On Aug. 29, 1945, an American B-29 piloted by a Lt. Jose H. Queen of Ashland, KY headed for Konan with a cargo of food and medical supplies. They were to be dropped over an Allied prisoner of war camp there. Four Yak fighters from nearby Hammung Airfield circled the B-29 and signaled the pilot to land on the too-small airstrip.

Queen did not obey and swung the big plane around to return to Saipan. Ten miles off the coast the Yaks opened up and the B-29 went down. All twelve disembarked safely but one Yak strafed and missed the radio operator. The Russians said they saw the American markings but since the Germans had used captured American planes they thought the Japanese might also. Remember this was two weeks after the official end of hostilities.

While the consensus of the Americans was that the Japanese could have been nowhere near producing an atomic bomb, that even the Germans were farther advanced, it is curious what this conclusion is based upon since no American has ever inspected the Konan facilities! It was a dangerous game to underestimate your enemy as the Allies found in December 1944 when the Ardennes Offensive (Battle of the Bulge) shocked the Americans to the realization that they could still lose the war. When the kamikazes became a horrifying reality in a divine wind over Okinawa there was no defense for them. There were no intelligence reports on either event to suggest the Allies were not taken completely by surprise.

Yoshio Nishina died in 1951. Since World War II the Konan area has been either in Soviet or North Korean hands so no look-see has ever been possible. It has been determined that heavy water was shipped out of the area in the 1950s to Russia.

At any rate, the Japanese could very well have had the capability of cobbling together a dirty bomb that did not create a chain reaction explosion but would rather dispense radioactive material into the vicinity of the target point, as the Germans could have done. Let us guess if they would have used it over Kyushu.

The hardware described here was real, tested and ready to go if not already in production and in service. Any more ambitious technological weaponry that would take longer to reach fruition is not considered as threats to invasion. These are.

(Into oblivion)

Mitchell Jamieson's "Invasion Craft Sicily"

Most of us feel that the government has never been completely up front with the public on many topics. Invasion Japan was another one. Giving them the benefit of the doubt it is certain that casualty estimates were low due to factors that were not considered due the complete lack of knowledge of their existence plus the probability that estimates were overly optimistic on purpose for planners to “sell” the plan to Truman and ultimately the public.

MacArthur, when asked by General Marshall in June 1945 for casualty estimates for President Truman figured for over 50,000 in the first 30 days and 117,000 for the first 90 days just for southern Kyushu! Truman gave the go-ahead without making a final decision on an invasion of Honshu. All these “educated” estimates were based on a probable 350,000 Japanese defenders when in fact in August there were already more than that many there in June with a probable 900,000 ready to defend by November.

These incorrect under-estimates would have proved disastrous. The other southern Japanese island of Shikoku is never mentioned in any invasion plans so perhaps it was to be by-passed. Hokkaido to the north is assumed to be an initial point of Soviet landing. But certainly Honshu, the main island, being many times larger in territory would have probably produced the greatest bloodbath in world history.

Kyushu is 17,135 square miles, Shikoku is just 7,258, Hokkaido is 32,246 and Honshu is a whopping 89,194 square miles. The dogged Iwo Jima campaign took place on the island of less than eight square miles in area for five weeks and cost 7,000 American and 22,000 Japanese lives. Okinawa is just 611 square miles and cost 12,000 American and 200,000+ Japanese dead (includes 100,000 civilians) during the 11-week fight. How long would it have taken to vanquish 900,000 fighting men in an area 17,000 miles square?

Even if Operation Olympic had gone off on November 1,,1945 against Kyushu, there is no way that it would have been over in 16 weeks in order to invade Honshu. It would have to have been a separate operation without the dependence of the American personnel and materiel engaged on Kyushu.

We are asked to imagine a home island roughly 28 times larger than Okinawa with proportionately scaled up defenses not all accounted for in Allied planning and think that there would have only been 46,000 American KIA. Next we are asked to envision THE home island, five times as large as Kyushu and think that just 200,000 would die out of a million casualties. We can see the entire campaign to subdue the home islands going into 1947 easily. Ten year mop up plans were envisioned when it was calculated that defeated troops would have slipped away into the mountains to commence guerilla warfare.

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