Plunge Pontificates

A place for my thoughts.

email me

Monday, May 09, 2005

Atomic Bomb Section 2 Japan’s defenses, what we knew then compared to what was reality

Return to the Table of Contents

Section 2 Japan’s defenses, what we knew then compared to what was reality

The Japanese understood that the war was lost. They had no thought of being able to pull victory from defeat; their only thought being how to make the defeat as painless as possible. With this in mind, they began to plan the defense of their home islands. They understood that Americans would only accept so many casualties and the more they inflicted, the easier it would be to demand conditions for their surrender. The military leaders of Japan were willing to sacrifice millions if it meant being able to maintain their current way of living, their culture and most importantly, their emperor. With the preparation they had made, it was likely they would have succeeded.

The US military was under a great misconception when it came to how Japan would defend the home islands. This seemed to be almost a disease with our military leaders when it came to planning battles with the Japanese. The closer we came to fighting in the home islands, the further our casualty and time projections were from reality. A good example of this was our fighting on Leyte.

Leyte was an operation to secure an area for the creation of airfields and as a jumping off spot for a larger operation. This is similar to what Operation Olympic was supposed to be. Most of what is remembered of this battle is MacArthur wading ashore, having triumphantly returned to the Philippines. What is forgotten is the nightmarish fighting it took to get to that point. MacArthur was supposed to have retaken Leyte with four divisions and have eight fighter and bomber groups striking from the island within 45 days of the initial landings. However, nine divisions and twice as many days into the battle, only a fraction of that airpower was operational because of the unexpected terrain conditions. The fighting on the ground had not gone as well as hoped for either. The Japanese even briefly isolated the headquarters and captured most of the airfield before reinforcements finally pushed them back into the jungle. There is no reason to suspect that it would have been any better at Kyushu.

The first time the military planners had any idea things were out of the ordinary was a report on July 29, 1945. While defenders of Kyushu were expected to climb to nearly 350,000, at the time, there were only supposed to have been 80,000 soldiers defending Kyushu. What they discovered was that there were over 200,000 defenders already in place and the numbers were growing quickly. This number would eventually reach 900,000 defenders, far above the 350,000 maximum that had been reported. Besides the ever expanding man power, Japan was learning US tactics just as fast as or faster than we were learning theirs.

Looking at records captured after the end of the war and declassified intercepts from that time revealed that Japan had pretty well surmised the US strategy for taking the home islands. Not only had the correctly identified the beaches we would be landing on, they had pretty well guess the entire timetable of the operation. This gave them a huge advantage when it came to preparing defenses. They didn’t waste anytime. Preparations to meet our soldiers on the beaches began in earnest. The thought of the kind of destruction their artillery would caused on our arriving troops in unthinkable. Having had months to prepare, Japan had zeroed in on all parts of the beach with their artillery, it would have been a bloodbath.

After taking the beaches, the US forces would have been up against defenses that would have made Iwo Jima and Okinawa look easy by comparison. The Japanese had become masters of cave and tunnel fighting. They dug gun positions, reinforced the walls with sever thicknesses of coconut logs, and covered the roofs with several layers of twelve-inch logs. Over the top they piled coral or sand and a layer of dirt. They then camouflaged the entire bunker with living trees and bushes. They could withstand a direct hit from all but the very largest of shells and bombs. The camouflage worked so well that soldiers often nearly stepped on them before realizing what they had come upon.

They were also masters at using natural caves, fortifying them and expanding them. Central living and command rooms were sometimes sixty feet inside the hills. Lateral tunnels led out to hillside openings and gun positions. Gun crews could pull their weapons inside in case they were discovered or came under heavy fire. On some islands, caves were found with up to nine levels of living quarters and could house 200 men. On Iwo Jima, one hundred caves were found in an area four hundred yards by five hundred yards. On Okinawa, the cave defense system was so extensive; it nearly cost the US the battle and gave one of the worst ratios of the entire war.

These caves were nearly impervious to naval bombardment, artillery or aerial bombing. They were built to support each other as well with interlocking fields of fire. They were protected on all sides and even after a hill was taken, they had nearly as hard of a time fighting their way down the back side because of the extensive preparations.

Despite all of our best efforts, there was very little in the way of innovation when it came to taking these prepared positions. A special project was even formed to try and discover new ways to defeat them, project “SPHINX.” Despite all best efforts, little was accomplished. Most of what was done was improving on what already worked, that being hand held and tank mounted flame throwers. Newer, longer range flamer throwers were developed to help the troops have some stand-off range. Flame thrower crews had some of the highest casualty rates of infantry men during the war.

Some felt these preparations by the Japanese were in vain since self-propelled 8-inch weapons and 155mm howitzers as well as tanks could destroy these bunkers. This is true of the original defenses set up by the Japanese early on, but they learned as well. This was discovered on Okinawa as the Japanese set up their defenses so that they had to be taken hand to hand.

Similarly, many have felt that Japan’s inadequate anti-tank weaponry would leave them vulnerable to a US attack. After all, Japan’s obsolescent 47mm anti-tank guns, quote: “could penetrate the M-4 Sherman’s armor only in vulnerable spots at very close range” and that the older 37mm gun was completely ineffective against the Sherman tank. Even with this, the Japanese had learned to adapt and become quite accomplished tank killers. During two actions on Okinawa, they were able to destroy 22 of 30 Sherman tanks. In one of those fights they managed to stop four tanks with shots from their “worthless” 47mm gun at 400 yards. The 37mm gun proved quite effective at immobilizing tanks at short range, leaving them vulnerable to other attacks. Outside of this, Japan was preparing thousands of suicide bombers who would strap anti-tank charges to their backs in order to destroy the tanks.

There were thousands of Japanese ready to commit suicide to save the home islands; far more than had been anticipated. The Kamikaze would be in the air on land and at sea. If a Kamikaze could kill only one American, it was worth the sacrifice; if they could destroy and entire ship, it would be bliss.

When the initial casualty estimates were created by Marshall and others, it was thought that there would be no more than 2,500 aircraft to oppose the landing. In reality, nearly 12,000 aircraft awaited the invasion fleets arrival. The Imperial Army planned to send these planes out in waves of up to 400 at a time. They would send more suicide planes in 3 hours than they did in three months at Okinawa. Their sole mission was to attack the troop transports. Many of these planes were flimsy bi-plane trainers. They were made of wood and cloth and as such, have been dismissed by those who would downplay Japan’s ability to defend themselves. The US military understood just how dangerous these training planes could be. A handful of these bi-planes were able to sink a US destroyer, the Callaghan on July 28th. It came as such a shock that word of it quickly reached the President. If such an insignificant plane could sink a fast moving, heavily armed destroyer, they would be lethal against a slow, nearly unarmed troop transport.

The Imperial Army had high hopes for their Kamikaze pilots. They projected that under favorable conditions, their pilots could destroy 50% of the invasion fleet before it ever reached the shores. On the low end, in bad conditions, they still felt that they could destroy 30% of the fleet.

Their Kamikaze hopes were not limited to the air; they also had manned suicide boats to throw at the invaders. While not strictly suicide boats, 2 types of submarines were available to attack invading ships. The survival rates for those serving on these submarines were so low that it might as well have been suicide. The first, the Koryu class carried 2 torpedoes. They had approximately 110 of these submarines ready for action. There was a smaller version of this called the Kairyu class which either had two torpedoes or, alternately, 600 kilograms of explosives packed in the nose for a suicide ramming mission. There were about 250 of these submarines available. Finally, about 1000 Kaiten were available. The Kaiten was basically a manned torpedo. Next were the Shinyo boats. These were single crew, small boats that carried two 120 kilogram depth charges. Their goal was to ram transport ships and blow them up. There were approximately 6,200 of these boats ready for use. Shinyo boats had been used in the Philippines with little success as they weren’t very fast and were highly visible. Finally, an unknown number of suicide swimmers were on hand to swim under landing craft and detonate explosives strapped to their bodies.

The final part of this intricate plan was the civilian population. At first, the thought was to evacuate the civilians until they quickly realized they had no place to move them to, no vehicles to move them with and nothing to feed them if they were moved. Therefore, in March, the Imperial Army decided to make the civilian population part of the reinforcements. Nearly 10,000,000 civilians lived on Kyushu. Every village and town was to form its own units. These units would be lead by selected leaders from the town. Soldiers would conduct training for the civilians 3-4 days a month. This was just enough training for them to understand the basics of weapons, guns, grenades, anti-tank tactics and a few other things. The citizens were also used to build the fortifications for the soldiers to fight from. Schools were closed and the students were mobilized to help with food production, the movement of materials, air-raid work and anything else to help them get ready for the impending attack.

At the end of March, the Patriotic Citizens Fighting Corps was formed. All men ages 15-60 and women 17-40 were subject to being called to duty. The term “cannon-fodder” comes to mind when thinking of these civilians. They had no uniforms, no weapons and little training. They were taught to use farming implements and other items to fight with. They were taught that if they were only able to kill one American, they had done their part to protect the homeland.

This is what awaited the American invaders: 900,000 soldiers, 12,000 kamikaze pilots, thousands of kamikaze boats, submarines, manned torpedoes and suicide swimmers. There were fortifications dug in over the entire island and the Imperial Army was determined to meet those soldiers that came ashore on the beaches. Millions of civilians stood ready to help the soldiers in anyway they could. It was setting up to be one of the bloodiest battles in history. If, for some reason, the battle had been delayed even further, the number of Japanese soldiers trained and waiting could have reached into the millions. Luckily, it never happened. It is easy to see how the estimates of Hoover could have even been considered conservative after realizing the full extent of Japan’s preparation.

While the Americans never realized the full extent of what was waiting for them, because of their ability to intercept and decode Japanese messages, a clearing picture was starting to form. For example, they soon realized that the number of soldiers they would be facing was much more than 350,000. Although they didn’t know the actual amount, their revised estimate was closer to 600,000 enemy soldiers. They realized their initial estimates were far from accurate and the more messages they intercepted, the more concerned they became. It got to the point where leaders started to seriously question the wisdom of continuing with Operation Olympic. Admiral Nimitz had early on felt the operation was ill conceived, others were now in agreement. Still, a better plan was not forthcoming and time was running short. Until the atom bombs were dropped, Operation Olympic was a go.

Section 3 The decision to drop the bomb / How the cities were chosen / Why there was no demonstration bombing