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Operation Olympic (later Operation Majestic) was the US code name for the invasion of Kyushu at the end of World War II. Operation Coronet was the name for the invasion of Honshu. After looking at a few sources, I think that overall the invasion would have failed.

Some people have asked if the Japanese military wouldn't have surrendered when the Americans proved they could land troops on the Home Islands. This is unlikely. At the major battles through the Pacific, the lowest percentage of Japanese soldiers killed was 97%. They did not surrender or even allow themselves to be captured if wounded. Tarawa and Makin both saw 99.7% casualties. These relatively minor objectives were fanatically guarded; the homeland of Japan would not be easily surrendered by people with that outlook.

The force balance for the Americans was also not favorable. At Iwo Jima, the force balance was 3.5:1 in favor of the US Marine Corps, yet casualties were 8:7 with heavier American losses. Okinawa had a 3:1 favorable ratio, but losses (not including US Navy losses from kamikazes and naval battles) were 1:1, including the loss of 57% of all tanks from suicide attacks with satchel charges. At Kyushu, the first attak was supposed to be with 9 divisions, against an expected Japanese force of 6 divisions, a 1.5:1 force ratio. In actuality, post-war records show that there were 14 division in Kyushu, giving the Japanese a roughly 1.5:1 advantage. Given that 3:1 odds gave 1:1 casualties, what would the ratio be in a 1:1.5 odds situation? The Honshu invasion would have been even worse, as 25 American divisions would have run into 65 Japanese, a 5:13 disadvantage. And while Army Intelligence believed Kyushu had only 2500 aircraft, records show they had over 10,000.

Nor were the planned invasion forces particularly strong. Demobilization had already begun, with the most experienced soldiers being first out. The worst hit large unit was the 45th Division, which had 83% of its men mustered out while they were transferring from the Atlantic to the Pacific Theater, to be replaced with other rookies from other units. Their organic artillery unit lost every officer except the CO, who was the only person that did not qualify for discharge. Other, smaller units lost up to 95% of their personnel. Training for the difference between European and Pacific combat ranged from a maximum of 20 days down to 9 days.

Given the lack of numbers and experience, I cannot believe that the invasion of Japan would have succeeded as planned. Estimated casualties run a wide gamut. MacArthur projected a loss of 124,935 soldiers in 120 days. Nimitz predicted 49,000 in 30 days. However, the Surgeon General of the Army estimated that Kyushu and Honshu would require two 90-day campaigns, with a total casualty list of 1,202,005 soldiers. This was based on the average casualty rate per thousand men per day for the seven amphibious campaigns (Guadalcanal, New Georgia, Leyte, Attu, Marshall Islands, Marianas Islands, and Palau). This number seems the most well-explained, and counts only ground forces. Including Nimitz's Navy numbers (based on casualties from kamikazes and Kaiten), a total expected casualty list for Americans only (not including Japanese casualties) is 1,244,005 soldiers. The expected Japanese casualties, assuming the low 97% casualty rate of Saipan, would be 1,149,450, just for ground soldiers. Of course, I expect Japanese casualties would have been much lower (perhaps 300,000), given their kill ratio at unfavorable odds. This would have led to a conventional stalemate, however, and would have necessitated use of atomic bombs as a measure of desperation, after having lost over a million Americans needlessly.

The US Military was well aware that Japan had about ten thousand aircraft remaining and some it its estimates went up to abut the 15,000 mark. No regard was made for where they where based in those estimates since it didn't really matter, planes flying from Honshu could easily reach the fleet supporting Olympic. In any case they wouldn't all be committed against the Olympic force.

Anyway your closing line is attempting to portray casualties as dead, that's not the case and the majority would be wounded. As for a stalemate, US planning didn't call for the capture of the whole island; we just wanted a large area to build airfields to bring P-47's and other bombers and fighters into range of Honshu. We also wanted Kagoshima bay as a forward naval base. Obtaining those objectives would be bloody but achievable. The terrain isn't as rough as some other islands we fought on and the Japanese lacked the elaborate fortifications found on them as well.

The really big battle would have been Coronet and on the Kanto Plain. It was more heavily fortified, and the troops protecting it far better equipped with very large concentrations of artillery and decent tanks. Shear weight of firepower could have brought an American victory at an incredible cost to both sides but I honestly don't think Coronet would be launched after the blood bath of Olympic. Nor was it a forgone conclusion that Olympic would be launched, there was a great deal of concern in the US military about the cost and its probability to success. Its quite likely, particularly as intelligence firmed up that the plan would be abandon in favor of a blockade. Some troops might however be landed in China to clear out Shanghi as was proposed as an alternative to Okinawa.

One major swing card is the atomic bomb. Plans where drawn up to use the weapons to bombard the beachheads on Kyushu should the initial attacks fail to end the war or simply not take place. By that point over a dozen bombs would have been available for the job. If those attacks took place with a couple more inland bursts t wipe out major IJA concentrations the invasion would be much less bloody for American forces. Long-term American losses from radiation would probably be low depending on how the bombs where busted.


A pure blockade of Japan as the method to bring an end to the war, was expected to result in the deaths of an additional 5-17 million Japanese mostly through famine and starvation over the winter of 1945-46. Though the number could easily reach 40 million depending on just how ruthlessly the IJA implemental it's planning to give no food to anyone outside the military. Some of these people would starve even with an invasion but the total death toll should be millions less even with the blood bath.

The historic atomic bombings saved millions at the minimal.

What about the Soviets? Werent they turning their eyes towards Japan after Hitler blew his remaining brain cell out? THat would have to figure in as well.

Darth Fanboy wrote:What about the Soviets? Werent they turning their eyes towards Japan after Hitler blew his remaining brain cell out? THat would have to figure in as well.

The mighty Soviet navy had one small cruiser and about ten destroyers in the Far East. It was beyond there ability to land on the Japanese home islands and they had no desire to do so. It's highly unlikely they'd have done anything more then their historic operations; indeed they might not even enter Southern Korea to keep away from American forces and logistically they couldn't go much deeper into China without a major investment in infrastructure. That was something they couldn't afford, the Union was in ruins and needed to spend its resources at home. The draw down of lend lease was especially making restoring full food and fuel production vital.

Sea Skimmer wrote:Nor was it a forgone conclusion that Olympic would be launched, there was a great deal of concern in the US military about the cost and its probability to success. Its quite likely, particularly as intelligence firmed up that the plan would be abandon in favor of a blockade. Some troops might however be landed in China to clear out Shanghi as was proposed as an alternative to Okinawa.

Even as late as the atomic bombings the armed forces were looking more and more towards the blockade option. Projections for OLYMPIC were becoming increasingly grim, if 'doable' and with overwhelming Allied naval firepower they might as well starve them out.

One major swing card is the atomic bomb. Plans where drawn up to use the weapons to bombard the beachheads on Kyushu should the initial attacks fail to end the war or simply not take place. By that point over a dozen bombs would have been available for the job. If those attacks took place with a couple more inland bursts t wipe out major IJA concentrations the invasion would be much less bloody for American forces. Long-term American losses from radiation would probably be low depending on how the bombs where busted.

Ugh. I can see the US cranking out nuclear devices as quickly as possible for tactical use, especially if we continue on to the Kanto Plain. Those Superforts with the Mk. 1 had better hope that they don't need to abort in salt water ....

phongn wrote: Ugh. I can see the US cranking out nuclear devices as quickly as possible for tactical use, especially if we continue on to the Kanto Plain. Those Superforts with the Mk. 1 had better hope that they don't need to abort in salt water ....

I know there was a plan to hit the beaches with nine bombs and hold several more in reserve in case of any major counter attacks or duds. I don't think the risk of US troops and shipping would be that great, if a plane has ditch in the ocean there's still going to be plenty of space clear of our forces. Though it does depend on when the nukes are used, that's something I don't know. If its H minus one hour then we could have problems, if its H hour minus one day then its a simply matter of pulling back the bombardment line back 10 miles or so.

Darth Fanboy wrote:What about the Soviets? Werent they turning their eyes towards Japan after Hitler blew his remaining brain cell out? THat would have to figure in as well.

Historically, the first Soviet attack occurred at roughly the same time as the dropping of the Nagasaki bomb. They were being opportunistic and trying to grab as much territory for as little fighting as possible. Their big plan was to go after the Kurile Islands if they got the opportunity, and to insist on being part of the Japanese occupation force.

Sea Skimmer wrote:The US Military was well aware that Japan had about ten thousand aircraft remaining and some it its estimates went up to abut the 15,000 mark. No regard was made for where they where based in those estimates since it didn't really matter, planes flying from Honshu could easily reach the fleet supporting Olympic. In any case they wouldn't all be committed against the Olympic force.

True, the generally accepted estimate within the military was 10,700 aircraft of all types. However, they believed far fewer were combat-capable, although the Navy was worried about obsolete trainers after biplanes were used as kamikazes. And, under Ketsu-Go, every plane was intended against Olympic, as the Japanese High Command recognized that if they lost Kyushu they could not continue the war. The main change was that the kamikaze fighters were instructed to aim at troop transports rather than aircraft carriers. A study showed that it took an average of four 5" cannon to down a single kamikaze, and few transports carried even a single 5" cannon. With 10,500 kamikazes attacking in continual waves, casualties would have been heavy even before reaching shore.

Anyway your closing line is attempting to portray casualties as dead, that's not the case and the majority would be wounded.

My apology, I reread my post and I did word that poorly. Estimated dead would be a little over 316,000 Americans, and over a million Japanese.

As for a stalemate, US planning didn't call for the capture of the whole island; we just wanted a large area to build airfields to bring P-47's and other bombers and fighters into range of Honshu. We also wanted Kagoshima bay as a forward naval base. Obtaining those objectives would be bloody but achievable.

True, but Olympic involved attacking at three separate, non-mutually supporting beachheads, at Ariake Bay, Miyazaki, and the west coast just above Koshiki-retto.

The terrain isn't as rough as some other islands we fought on and the Japanese lacked the elaborate fortifications found on them as well.

The terrain was "a complex jumble of small lowlands and low but rugged uplands" (CCS 417/11), with only three plains by the landing beaches, each roughly three to ten miles wide and twenty to thirty miles long. The rest of the island consisted of heavily rugged terrain impassable to armored vehicles. The only passageways between them are between one and five miles wide. The units on Kyushu had 76 days to dig in between when the surrender occurred and the actual planned invasion (not including the time they had already been there), compared to the 50 to 100 (depending on unit) of Okinawa. Indeed, one battalion at Ariake Bay had dug over 16 kilometers of tunnels with firing positions over the beach. Japanese estimate was that the Ariake defenses were ~85% complete at surrender, and the other defenses ~40% (they had expected Ariake to be hit hardest, which was true, and had planned accordingly).

Another thing to look at is the morale effect of American casualties. The 316,000 deaths that were the Surgeon General's best estimate would have more than doubled the dead for the entire war (both theaters), and American public opinion was already leaning towards the war having gone on too long.

I mostly intended this as a discussion of why the Hiroshima/Nagasaki bombs were necessary, though apparently I was more asleep during my initial post than I thought, as I never mentioned that .

The Dark wrote:Historically, the first Soviet attack occurred at roughly the same time as the dropping of the Nagasaki bomb. They were being opportunistic and trying to grab as much territory for as little fighting as possible. Their big plan was to go after the Kurile Islands if they got the opportunity, and to insist on being part of the Japanese occupation force.

That attack was in planning long before the bombs where dropped and was part of the Soveit's pledge to attack Japan six months after the war in Europe ended. As for the Kuril's, the Russians did capture them. They had no intention or capability to go further and America would be quite able to tell them to go to hell about being a part of the occupation force.

True, the generally accepted estimate within the military was 10,700 aircraft of all types. However, they believed far fewer were combat-capable, although the Navy was worried about obsolete trainers after biplanes were used as kamikazes. And, under Ketsu-Go, every plane was intended against Olympic, as the Japanese High Command recognized that if they lost Kyushu they could not continue the war. The main change was that the kamikaze fighters were instructed to aim at troop transports rather than aircraft carriers. A study showed that it took an average of four 5" cannon to down a single kamikaze, and few transports carried even a single 5" cannon. With 10,500 kamikazes attacking in continual waves, casualties would have been heavy even before reaching shore.

They couldn't all come at once, nor would all of them be serviceable by 1946, the USAAF intended to begin a carpet-bombing campaign of every airfield it could find. They're where hundreds but it would inflict damage. With a thousand odd B-24, 17's and 29's attacking that's a lot of dead airfields.

Loss would be heavy but the fleet could field several thousand heavy anti aircraft guns and would have several thousand fighters flying cover. Contrary to what you've stated every US transport had at least one five inch gun and most had two to four. We'd also have a record level of VT ammo, off Okinawa the mix was about 50/50 VT and conventional while off Japan it was expected to be more like 75% VT.

]My apology, I reread my post and I did word that poorly. Estimated dead would be a little over 316,000 Americans, and over a million Japanese.

Only a million Japanses might die in the fighting, but when we factor in those who starve that 5-17 million figure comes back around..

True, but Olympic involved attacking at three separate, non-mutually supporting beachheads, at Ariake Bay, Miyazaki, and the west coast just above Koshiki-retto.

I think twenty five battleships will keep the troops from being overrun, just a hunch. The Japanese would have very little mobility, which means the marines and Army troops will never face more then a fraction of them at once.

The terrain was "a complex jumble of small lowlands and low but rugged uplands" (CCS 417/11), with only three plains by the landing beaches, each roughly three to ten miles wide and twenty to thirty miles long. The rest of the island consisted of heavily rugged terrain impassable to armored vehicles. The only passageways between them are between one and five miles wide. The units on Kyushu had 76 days to dig in between when the surrender occurred and the actual planned invasion (not including the time they had already been there), compared to the 50 to 100 (depending on unit) of Okinawa. Indeed, one battalion at Ariake Bay had dug over 16 kilometers of tunnels with firing positions over the beach. Japanese estimate was that the Ariake defenses were ~85% complete at surrender, and the other defenses ~40% (they had expected Ariake to be hit hardest, which was true, and had planned accordingly).

The Japanese had a huge timber shortage; I seriously doubt most positions could withstand bombardment. Elaborate tunnel networks can be useful, but the Japanese lock up far too many troops inside such positions and that seriously limited their effectiveness. That whole defeat in detail thing comes up again.

Sea Skimmer wrote:

True, the generally accepted estimate within the military was 10,700 aircraft of all types. However, they believed far fewer were combat-capable, although the Navy was worried about obsolete trainers after biplanes were used as kamikazes. And, under Ketsu-Go, every plane was intended against Olympic, as the Japanese High Command recognized that if they lost Kyushu they could not continue the war. The main change was that the kamikaze fighters were instructed to aim at troop transports rather than aircraft carriers. A study showed that it took an average of four 5" cannon to down a single kamikaze, and few transports carried even a single 5" cannon. With 10,500 kamikazes attacking in continual waves, casualties would have been heavy even before reaching shore.

They couldn't all come at once, nor would all of them be serviceable by 1946, the USAAF intended to begin a carpet-bombing campaign of every airfield it could find. They're where hundreds but it would inflict damage. With a thousand odd B-24, 17's and 29's attacking that's a lot of dead airfields.

SOP in 1945 was to keep all planes at least 3 kilometers away from airfields. Photo recon missions showed individual planes up to 5 miles away. Through 1945, more aircraft were manufactured then destroyed by bombing. They also never intended all the planes to show up at once, but rather have a hundred or so come every couple hours.

Loss would be heavy but the fleet could field several thousand heavy anti aircraft guns and would have several thousand fighters flying cover. Contrary to what you've stated every US transport had at least one five inch gun and most had two to four. We'd also have a record level of VT ammo, off Okinawa the mix was about 50/50 VT and conventional while off Japan it was expected to be more like 75% VT.

I was running off a quote that states "Amphibious ships...[and] lesser craft were well equipped if they boasted one five-inch gun with no sophisticated controls." The information the author of that statement used came from reports by John C. Reilly Jr. and Y'Blood. And VT ammo was sometimes more trouble than it was worth. The Callaghan was sunk because it used VT ammo that did not go off and was sunk by an attack group of 8 biplanes (CINCPAC Report plus ULTRA intelligence for number of biplanes). The VT ammo was not reliable. And there would be large numbers of aircraft (estimated 10,000), but they would have little reaction time, as the kamikaze were instructed to hug the terrain and not fly over open water.

]My apology, I reread my post and I did word that poorly. Estimated dead would be a little over 316,000 Americans, and over a million Japanese.

Only a million Japanses might die in the fighting, but when we factor in those who starve that 5-17 million figure comes back around..

True, I was merely thinking of combat casualties.

True, but Olympic involved attacking at three separate, non-mutually supporting beachheads, at Ariake Bay, Miyazaki, and the west coast just above Koshiki-retto.

I think twenty five battleships will keep the troops from being overrun, just a hunch. The Japanese would have very little mobility, which means the marines and Army troops will never face more then a fraction of them at once.

Battleships can't safely fire into melee. CAS might be possible, but the Ketsu-Go plan included abandoning the defenses until the preliminary shelling stopped (Americans had gotten very predictable on time of shelling), then reoccupying between the end of shelling and the first landing waves. Without an actual occurrence, success is impossible to predict, but the first wave would probably do fairly well. Reserves would be easier to interdict. And all the battleship shelling of Okinawa had little effect.

The terrain was "a complex jumble of small lowlands and low but rugged uplands" (CCS 417/11), with only three plains by the landing beaches, each roughly three to ten miles wide and twenty to thirty miles long. The rest of the island consisted of heavily rugged terrain impassable to armored vehicles. The only passageways between them are between one and five miles wide. The units on Kyushu had 76 days to dig in between when the surrender occurred and the actual planned invasion (not including the time they had already been there), compared to the 50 to 100 (depending on unit) of Okinawa. Indeed, one battalion at Ariake Bay had dug over 16 kilometers of tunnels with firing positions over the beach. Japanese estimate was that the Ariake defenses were ~85% complete at surrender, and the other defenses ~40% (they had expected Ariake to be hit hardest, which was true, and had planned accordingly).

The Japanese had a huge timber shortage; I seriously doubt most positions could withstand bombardment. Elaborate tunnel networks can be useful, but the Japanese lock up far too many troops inside such positions and that seriously limited their effectiveness. That whole defeat in detail thing comes up again.

The Japanese also didn't have much timber on Okinawa, yet those positions were virtually untouched by shellfire. As I stated in my original post, Okinawa had even casualties despite a 3:1 manpower advantage by the Allies. At Kyushu, the manpower was in the Japanese' favor, and they had a superior defensive network to Okinawa. American armor would be bottled up in narrow plains, and volunteer units had been trained in suicide attacks with large explosives to disable American tanks. I think the best that can be said is that any outcome would be uncertain, as there are many variables, some of which favor each side.

As an aside, I believe that it has been stated that the Okinawa tunnels were a large inspiration for the Viet Cong, so apparently we can lay partial blame on WWII for that problem as well.

The Dark wrote:SOP in 1945 was to keep all planes at least 3 kilometers away from airfields. Photo recon missions showed individual planes up to 5 miles away. Through 1945, more aircraft were manufactured then destroyed by bombing. They also never intended all the planes to show up at once, but rather have a hundred or so come every couple hours.

We had a lot of bomber and fighter-bomber missions to spare. Aerial reconnaissance could find the fields and trace the dispersion points. Bombing didn't destroy many planes in 1945 because the B-29's where still busy burning out cities and the mass of US fighter bombers and B-17's and B-24 weren't yet established in forward bases and flying missions.

And if they come in well spaced waves we get the Falklands with a potentially overwhelming air force being worn away without accomplishing to objectives through a failure to mass sufficient planes on target at once. Ships had time to replenish their ready ammo, and a new CAP could be cycled through.

I was running off a quote that states "Amphibious ships...[and] lesser craft were well equipped if they boasted one five-inch gun with no sophisticated controls." The information the author of that statement used came from reports by John C. Reilly Jr. and Y'Blood.

Its quite wrong. A typical armament for a mere Liberty ship in 1945 was a single 5 inch gun aft and a three inch gun forward. Ships converted to transports generally had two to four 5 inch guns.

And VT ammo was sometimes more trouble than it was worth. The Callaghan was sunk because it used VT ammo that did not go off and was sunk by an attack group of 8 biplanes (CINCPAC Report plus ULTRA intelligence for number of biplanes). The VT ammo was not reliable.

A single example proves nothing; poor ammunition handling could have been at fault. The VT fuse had a very high reliability and a huge leap in lethality over timed fuses and consistently demonstrated it from 1942 both in the Pacific, Northern Europe and the Mediterranean.

And there would be large numbers of aircraft (estimated 10,000), but they would have little reaction time, as the kamikaze were instructed to hug the terrain and not fly over open water.

That's what the AEW aircraft and shear mass of defending fighters was for. Unlike Okinawa a huge mass of land based P-47's and P-51's would be available to protect the fleet and fly wider patrols.

]My apology, I reread my post and I did word that poorly. Estimated dead would be a little over 316,000 Americans, and over a million Japanese.

Only a million Japanses might die in the fighting, but when we factor in those who starve that 5-17 million figure comes back around..

True, I was merely thinking of combat casualties.

quote]Battleships can't safely fire into melee. CAS might be possible, but the Ketsu-Go plan included abandoning the defenses until the preliminary shelling stopped (Americans had gotten very predictable on time of shelling), then reoccupying between the end of shelling and the first landing waves. Without an actual occurrence, success is impossible to predict, but the first wave would probably do fairly well. Reserves would be easier to interdict. And all the battleship shelling of Okinawa had little effect.

Actually battleship fire on Okinawa was devastating when properly directed, and your notice that at Okinawa the Japanese did not defend the waterline or anything close too it. That made them much less vulnerable but also makes a victory impossible ,once American forces are established onshore nothing will dislodge them.

Evacuating defenses until the bombardment ceased wasn't a remotely new tactic the Pacific war so don't try and tote it as once. You need fortifications to return too, and with ships carefully picking out targets for a prolonged period before the invasion not many will remain. Then your troops are stuck in the open and then they die.

The Japanese also didn't have much timber on Okinawa, yet those positions were virtually untouched by shellfire.

That is because most fire was not directed against their actual locations and later targets where often in defilade. When heavy naval gunfire hit it destroyed.

[/quote]
As I stated in my original post, Okinawa had even casualties despite a 3:1 manpower advantage by the Allies. At Kyushu, the manpower was in the Japanese' favor, and they had a superior defensive network to Okinawa. American armor would be bottled up in narrow plains, and volunteer units had been trained in suicide attacks with large explosives to disable American tanks. I think the best that can be said is that any outcome would be uncertain, as there are many variables, some of which favor each side. [/quote]

Suicide attacks against armor is nothing new, we built up a vast stock of flamethrowers tanks because of that. And one variable has been ignored. All those clever Japanese plans also called for the use of poison gas in the invading troops. The moment that happens the US will unleash the huge stockpile of mustard gas bombs it had been building up during the war and forward deployed in case of such a contingency.

Do you know what happens to troops in deep fortifications who generally lack basic gas masks when there hit with blister agents? Hint: The result is generally total annihilation

They planned to gas US troops? Thats fucking insane.


How were the troops equipped as for protection equipment?

Howedar wrote:They planned to gas US troops? Thats fucking insane.


How were the troops equipped as for protection equipment?

We universally issued masks, and the Japanese mostly produced choking and blood agents the soldiers and marines would have fairly good protection. However some blood agents rapidly eat through the protective filters, so a second attack might inflict heavy losses on previously exposed troops. Luckily the Japanese did not produce very much mustard gas, which of course hits you skin as well.

We also did have a limited supply of full chemical protective suits that would stop mustard, however to call them ovens is an understatement and only some special engineering and infantry units ever got them. The only time I'm aware that they got used was at Normandy, there was a concern the gases might be beached so we wanted to be sure the first wave specialists that needed to clear obstacles for rest would survive.

The US counterstrike would use mostly mustard. Many regular Japanese units had masks as well, but they made up only a small fraction of Japanese forces and I doubt they had decent filters, they need replacement often even without use. The horrible skin burns that would result from am mustard gas attack even aginst masked troops would be overwhelming fatal to Japanese forces with there near total lock of medical facilities.

One big problem would be if they delivered gas against our shipping, its unlikely but possibul. Decontaminating a ship was found to be impossible in 1920's experiments and any ship heavily affected would have to be scuttled.