In popular understanding, we think of intelligence operations as “code breaking.” But those were always later developments. The first step was listening in on enemy transmissions. Intercepts were collected by ground stations, ship-based stations, aircraft with radio monitoring gear, and even submarines. Once the encrypted communications were intercepted, even when messages couldn’t be decrypted, analysts studied call signs, frequencies, message traffic volume, transmission times, and transmission locations. Early in the war these “signal intelligence” (SIGNIT) operations were sophisticated enough to reveal patterns such as unit locations, movements, and order of battle. The early June 1942 Japanese attack on Midway was “known” through traffic analysis without the benefit of code breaking. This was done by the Hawaii based Station Hypo.

When it became clear that the Mariana Islands (Saipan, Tinian and Guam) had been taken over by the Allies, the Imperial Japanese Army (IJA) Journal recorded: “We can no longer direct the war with any hope of success. The only course left is for Japan’s one hundred million people to sacrifice their lives by charging the enemy to make them lose the will to fight.”  The Japanese military would implement that plan in the Special Attack Forces and would promote their sacrifice to the general population as a means of propaganda and to animate and reinforce the resolve of the Japanese people to be willing to sacrifice their lives for the Emperor.

The air battles at Philippine Sea in June 1944 decimated the Japanese Navy’s (IJN) aviation capability for aircraft carrier based operations. The IJN and IJA aviation units (planes and pilots) were further reduced by the air battles over Formosa (Taiwan) in October 1944. Between the two engagements, Japanese losses were approximately 800 planes and 900 airmen. The critical loss was skilled and experienced pilots. Japan’s aircraft production peaked at about 2,572 planes per month in September 1944, then began to decline from late 1944 into 1945 as strategic bombing increasingly disrupted output, though production hovered above 1,000 combat aircraft per month until mid‑1945. They could replace the planes more easily than the aviators.

At the start of WWII, Japan had 2,600 airplanes of all types. The average pilot had 500-700 flight hours. They reached a peak in January 1944 – approximately 5,600 planes and despite the 1944 losses, they began 1945 with some 4,100 planes. But by 1945 the average Army pilot had only 130 hours of flight time; a Japanese naval aviator had 275 hours on average. The net effect was an enfeebled air combat capability.

By late 1943 Japanese officers began to see the slow devolution of capability and began to advocate for organized suicide attacks. There was no consensus on the idea.  On May 27, 1944 an Army pilot intentionally crashed into an allied ship (IJN Journal). Within a month, as Saipan was about to fall, Fleet Admiral Prince Hiroyasu (former chief of the Naval General Staff) openly spoke: “Both Army and Navy must think up some special weapons and conduct the war with them.” “Special weapons” was the Japanese euphemism for suicide weapons. Only a year before the idea had been rejected.

The first organized air kamikaze attack occurred on October 25, 1944 at the Battle of Leyte Gulf (Sommar) in the Philippines against Task Force Taffy 1 which consisted of escort carriers and destroyers. The Japanese force was led by Lt. Seki Yukio and Hiroshi Nishizawa, two of Japan’s premier naval aviators; each of the ace aviators.  Eighteen kamikaze took off; six returned having failed to find a target – a common feature on such missions. The remaining dozen scored damaging hits on the escort carriers Santee and Kitkun Bay, killing 17, but sank the St. Lo leaving 114 dead.

Nishizawa’s role was observer. He returns to base and reports the great success of the mission. What was to that point an idea, now became a tactic. The experience at the Battle of Philippine Sea revealed two major advantages held by the US Fleet: aviation and anti-aircraft defense.  By the summer of 1944, the  US Navy had superior aircraft, better pilots, and superior numbers – all being controlled by the first Combat Information Center (CIC) that coordinated sorties, targets, and missions by integrating radar and message traffic. In 1942 “first detect” range was ~30 miles. By 1944 that range was extended to 100 miles making the first intercept miles away from the aircraft carriers. If they got past that gauntlet, the enemy pilots faced the next advantage.

By 1944 the carriers were protected by defense-in-depth from destroyers to light cruisers that were intentionally outfitted, not for ship-to-ship engagement, but for anti-aircraft (AA) defense. These ships were “armed to the teeth.” In addition, the VT fused shells (proximity weapons) increased the lethality 5-7 times. In 1942 the fleet was capable of firing 32,000 lb/minute in AA weapons fire. In 1944, with the advent of the VT-fused shells, the fleet was capable of effectively firing 575,000 lbs/min.

In a sad calculus of thinking, all the above made clear that a Japanese battle plan to mount a torpedo or dive bomb attack against the US Fleet was not likely to succeed and had an almost zero chance of the pilot returning. The conventional mission gave way to the reality of the one-way mission, now almost a given – and from this was born the battle plan of the divine wind, kamikaze.

What are we seeing?

For the survivors of Taffy 1’s ships they had to wonder what they had just seen. Were the pilots intentionally crashing into ships? Word spread rapidly through the 3rd Fleet. From Admiral to sailor all began to wonder how could these aviators were suddenly suicide bombers? What could possibly drive them? The answer to that question lay deep inside the military culture of Japan.

Kusunoki Masashige was a 14th-century samurai and retainer of Emperor Go-Daigo. He was known for his absolute loyalty to Emperor Go-Daigo during the struggle to overthrow the Kamakura shogunate. He was admired for his strategic brilliance, his defensive stand at Chihaya Castle, and—most famously—his willingness to obey the emperor’s command to fight a hopeless battle at Minatogawa (1336). Knowing he would die, Kusunoki went into battle anyway, sacrificing himself for imperial loyalty. He died in combat along with his brother and many of his men. Because of this, he came to be revered as the archetype of the loyal retainer who sacrifices himself for duty and country.

In the early 20th century, especially during the rise of State Shintō and Japanese militarism, Kusunoki was lionized as a national hero and portrayed as the embodiment of bushidō: selfless loyalty, obedience, and honor in death. A massive bronze statue of him, erected in 1900, stands in front of  the Imperial Palace in Tokyo, symbolizing martial devotion to the emperor. By the 1930s and 40s, Kusunoki was the center piece and model of what it meant to be, not just in the Japanese military, but as a citizen of Japan. His story and his devotion to the Emperor was part of school textbooks and state propaganda. He was the personification of a Japanese person: a warrior who placed loyalty above life itself. His famous dying words lamenting “Would that I had seven lives to give for my country” (“Shichishō Hōkoku”). School children memorized his words and were repeatedly taught his story with his statue becoming a pilgrimage site.

Kusunoki gave a historical precedent that made the kamikaze sacrifice seem like part of a long Japanese tradition, not an aberration. By portraying suicide attacks as the modern version of Kusunoki’s doomed battle, leaders could frame the kamikaze not as desperate measures but as honorable continuity. “Seven lives for the emperor” became a rallying cry for the kamikaze pilots.

This was the ethos of the WW II Japanese military and citizenry. Now the aviators were urged to live and die in the same spirit. One need only search for internet images of kamikaze unit flyers. Most of them show young men in their aviator kits with samurai swords. 

What the US sailors were seeing was the spirit of Kusunoki Masashige, not on horseback, but piloting lethal, ship-killing missiles.

Okinawa

On April 6, 1945, the first wave of ten coordinated kamikaze attacks began to hit the U.S. Navy’s Fifth Fleet off the coast of Okinawa. Ships in the Fifth Fleet had experienced suicide attacks before — but never on such a scale. The terrifying sight of Japanese pilots diving their planes into ships would become common over the next two and a half months. Aircraft carriers and battleships were supposed to be the main targets, but the ships that suffered the most damage were the destroyers and smaller vessels assigned to protect the fleet from incoming attacks. And as the war continued, troop ships, tankers, and supply ships were increasingly targeted.

From October 1944 until the end of the war, there were some 3,000 sorties flown. This resulted in the loss of 3,389 naval personnel. In total, by the end of July 1945 kamikaze attacks damaged 350 ships (including  30 aircraft carriers) and sank 47.

Invasion Planning and Threat of Kamikaze

According to the postwar Strategic Bombing Survey, Japanese airpower at the end of the was: 5,350 aircraft (combat, advanced trainers and primary trainers) assigned to Special Attack units with an additional 5,300 not yet assigned. In addition, there were another 7,200 aircraft in need of repair. Operationally there were as many as 10,000 available aircraft and some 18,000 pilots with at least 70 hours of flight experience. The survey also noted that there were 1 million barrels of aviation fuel on hand. The planned kamikaze missions were only expected to require 50,000 barrels.

Advanced planning for the coming allied invasion of Kyushu included suicide sorties in waves of 300 to 400 planes every hour with the primary targets being troop transports. This would be more kamikazes in three hours than sent against the Okinawa campaign in three months.

There would be a major difference between Okinawa and Kyushu. The Okinawa attacks required long flights over open water through rings of scouting places, radar picket ships, and combat air patrols. The waves of attacks were always seen in advance, weather/cloud cover permitting. The experience in the Philippines was different: shorter flights, ground clutter affecting radar, and other topographic factors lead to more stealth and thus surprise attacks.  At Kyushu the troop transports would lay in conventional disposition close to the coast allowing the kamikaze to burst upon the scene with little warning.

That being said, ULTRA identified most of the kamikaze bases and these would be subject to advanced air attack. This was something that the Japanese realized and initiated new efforts of dispersal and concealment away from the base. They estimated that no more than 20% of aircraft would be destroyed on the ground prior to missions. In addition new production of suicide planes were wood construction: easy to move, shorter runways needed, not easily detected by radar, and far less vulnerable to the proximity fused antiaircraft shell.

Clearly, the airborne kamikaze attacks were a significant threat to lives and shipping. But these were not the only Special Attack units. Other units/means included:

• Shinyo – Suicide Motorboats. Small, fast, one-man boats packed with 250–300 kg of explosives in the bow. Around 6,000 were built.
• Kaiten – Manned Suicide Torpedoes. These were modified Type 93 “Long Lance” torpedoes with a cockpit for a pilot. The unit was launched from submarines with the pilot guiding the weapon to its target. They had limited success but were responsible for sinking the USS Mississinewa (AO-59) in November 1944.
• Ohka (“Cherry Blossom”) – Rocket-Powered Manned Bomb. Small, rocket-propelled glide bomb carried under a bomber, piloted by a kamikaze. The Ohka was to be released near the target to glide/rocket into a ship at high speed.Used mainly in 1945, especially against US ships off Okinawa.
• Fukuryu and Maru Dai – both were “frogmen” with either explosive packages or mines to attach to ships.

This all indicates the extent of the June 1944 decision to develop “special weapons.”

That is the mindset and future facing Kyushu invasion planners. What follows is the experience of those who survived kamikaze attacks.

Shipboard perspective (Source: PBS – American Experience: Victory in the Pacific, “Kamikaze”)

One such destroyer was the U.S.S. Newcomb. The Newcomb had seen combat before, at the Mariana Islands, Peleliu, Palau and in the Philippines. But it was at Okinawa that she would fight her fiercest battle. On board the destroyer was 21-year-old John Chapman, a First Class Boatswains Mate, and gun captain of a five-inch gun. Facing enemy pilots willing to give their lives to sink his ship struck him as almost incomprehensible.

“It didn’t make you feel good. I don’t know whether that’s ‘terrified’ or not, but it didn’t make you feel too well because of it, knowing that people would do a thing like that. You know, people we had always known weren’t like that. They were brave people and so forth, and they fight, but weren’t someone to just deliberately take their lives to take yours.”

Watching Kamikazes Attack. More than 300 kamikazes departed Southern Kyushu on April 6. Their target was the U.S. Fifth Fleet stationed in support of the battle being waged on Okinawa. As the Japanese pilots approached, they broke off into smaller attack groups. John Chapman was at his gun post at the stern of the U.S.S. Newcomb.

“There was probably 45 planes in the air. Well, it was a scary situation, because you knew that they were going to dive on you. You could be firing on the aircraft, and they’d come right on, just keep coming right on through that. And you’d see pieces flying over the planes and everything else, and they’d just keep right on a-coming.”

A Roaring Inferno. The Newcomb shot down four enemy planes. Five others hit the ship. Those on board who were not killed or injured fought desperately not only to put out the raging fires and repair damaged engines, but also to keep firing at an enemy dead set on sinking them. The scene aboard the Newcomb was repeated on many vessels of the fleet that day.

“It was hot. The fires were just raging totally out of control. Between the bridge and the afterdeck house, that’s a big percent of the ship. It was nothing but a roaring inferno. The flames were shooting. They said [it] was high as 1,000 feet in the air off the Newcomb.”

Overboard. Firefighters battling the raging fires forced John Chapman and an injured friend to jump overboard. There was no space left for them on the stern to remain. Chapman handed his life belt to the injured friend and, once in the water, towed him to the safety of a lifeboat. They were later rescued along with many others in the waters off Okinawa.

Aftermath. Ninety-one sailors were killed or wounded on the U.S.S. Newcomb. Many of those who were injured suffered devastating burns. But despite suffering at the hands of the five kamikazes, the crew of the Newcomb kept their vessel afloat and earned the Navy Unit Commendation and eight battle stars for World War II service. John Chapman would earn a bronze star for his service; years later, his view of his heroism is clear-eyed:

“People try to glorify wars and so forth. There’s people that do outstanding things, but there’s nothing really glorious about a war. You do wars to protect your country if you have to, and that’s the only time you should ever do it.”

Terrible Naval Losses. Nine more waves of kamikaze attacks hit the fleet off of Okinawa before the battle came to an end. Almost 2,000 Japanese pilots would willingly lose their lives in these attacks.

By late June 1945, close to 5,000 U.S. sailors had been killed and 5,000 more wounded by the Japanese suicide pilots. Thirty ships had been sunk and almost 400 others were damaged. The attack on the Fifth Fleet off Okinawa would mark the worst losses of World War II for the U.S. Navy.

Source: PBS – American Experience: Victory in the Pacific, “Kamikaze” (https://www.pbs.org/wgbh/americanexperience/features/pacific-john-chapman/) 

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives.

During the early 1945 the war in the Pacific was inexorably drawing closer to the Japanese home islands. There were two major campaigns that were initiated in the Winter and early Spring:

• Iwo Jima (Feb 19 – Mar 26, 1945)
• Okinawa (Apr – Jun 1945)

Each of these campaigns were within range of Japanese aviation forces based on Kyushu and Honshu. A critical element of the above campaigns was the suppression of those aviation forces. That work fell to the U.S. Navy. 

The Navy, freed from most major fleet engagements after the Philippine Sea and Leyte Gulf, shifted to directly attacking the Japanese homeland with multiple purposes in mind: suppression of aviation support for Okinawa and Iwo Jima; damage to industrial facilities, disruption of coastal shipping; elimination of the remnants of Japan’s Combined Fleet; disruption of rail-ferry links between Hokkaido and Honshu; cutting a key source of food shipments; disruption of the rail supply system leading from the Tokyo industrial area southward toward Kyushu and; presenting to the Japanese people that the Allied Forces could strike at will.

In February 1945 the first major aircraft raids were conducted in the Tokyo area. The objective was to neutralize Japanese air power prior to the Iwo Jima landings. Carrier aircraft from Task Force 58 struck Tokyo, Yokosuka, and nearby airfields, shipyards, and factories. Over 500 Japanese aircraft were destroyed (majority on the ground), some naval units damaged, including the carrier Amagi. 

In the months following, US carriers pre-emptively struck Japan in preparation for the Okinawa landings. From April through June the US carriers supported the ongoing Okinawa operations by striking airfields in nearby Japan when necessary. Finally, by July 1945 Okinawa was secure and the full attention of the  US and British fleets (carriers, battleships, cruisers and destroyers) could turn their attention to shore bombardment of Japan from Kyushu in the south to Hokkaido in the north with Honshu in between. While their reach was limited their accuracy was deadly. In late July the industrial and electronics-producing city of Hitachi was subject to shore bombardment. A key factory that had avoided destruction by air assault was level with four hits from the 16-inch guns of a US battleship.

While the July 1945 naval bombardment received little coverage, there are several key elements revealed regarding the state of the war in the Pacific:

• Naval ships (carriers, battleships, cruisers, etc.) could approach the coast with impunity. By way of analogy, Japan was a medieval castle under siege. Outside the “walls” the Allied forces were free to operate; inside there was nothing to do except endure
• At the same time, the Naval aviators and US Army Air Force bombers also operated without restriction.
• The Allied fleet was free to aggressively sweep Home Island waters searching for Japanese warships and merchantmen. 

The primary focus of this undeterred bombardment from sea and air was focused on Operation Olympic, the invasion of Kyushu. Targets included:

• Pre-invasion bombardment of potential Kyushu landing beaches and the inland areas immediately adjacent to the beaches to begin the “softening” on the in-depth defense and on-going construction of the same.
• Japanese airfields and aircraft production sites in order to minimize the operational capacity and ability to mount kamikaze attacks during
• Transportation lines and hubs that would be used to supply/re-supply Kyushu (Japan was particularly dependent on coast shipping and railways as they had little to no developed roadways)
• Coastal shipping and merchants attempting to import supplies – including food – to Japan

At this point, by any effective measure, Japan was under an almost complete blockade. Only the Korea-Japan shipping channels were available and only under the cover of weather which limited the ability of the allies to find and track the merchants.

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives.

The capture of the Saipan  and Tinian (July 1944) gave the allies air bases for the B-29 Super Fortress bombers.  The home islands of Japan were within range and the Allies were now able to initiate sustained bombing of Japan without risking aircraft carriers which would have operated within range of Japanese counter attacks. The B-29 raids began on November 24, 1944. Tokyo was the first target. It consisted of 111 B-29s striking the Musashino aircraft engine plant on the outskirts of Tokyo. The raid was executed as a high-altitude precision raid (but with little effect). As noted in a previous post, the Allies faced major challenges over Japan: high-altitude jet stream winds disrupted bombing accuracy; weather conditions, especially cloud cover, reduced visibility. 

The bombing campaign was focused on Japanese cities. The goal was to destroy key industrial and military targets such as aircraft factories, shipyards, and transportation hubs. The strategy was modeled on the efforts against Nazi Germany which concentrated production in large factory settings.  Japanese industry was decentralized, with small workshops spread throughout urban residential areas. These workshops were as small as home-based, then feeding large operations, still in residential areas, again working up the supply chains to large operations, often located on the edge of residential areas. While there were critical war production located apart from residential areas, e.g. shipyards, other production (ammunition, airplane assembly, weapons, etc) took place in the labyrinth of major city residential areas.

There was an early phase of B-29 bombings on the Japanese home islands as part of Operation Matterhorn. These were planes launched from China. The airfields in China were highly vulnerable. Supplies and logistics had to be flown over the Himalaya Mountains. There were no accompanying fighter escorts. Targets were typically industrial or military facilities near western coastal cities (e.g., steel works, shipyards, aircraft plants). Damage was limited due to small bomb loads, long flight distances, and weather conditions. All in all, the raids were psychologically unsettling, but neither tactically or strategically valuable. 

That began to change in late November 1944.

Before we delve into the aerial bombing campaign, we should consider an event which was seared into the minds of Tokyo and Yokohama residents – an event which shaped emergency preparedness: the 1923 Tokyo earthquake, also known as the Great Kantō Earthquake (the Kantō plane is the broad area on Honshu island that encompasses some of the great cities of Japan)

The earthquake struck on September 1, 1923, at noon when people were cooking lunch. The ~8.0 magnitude earthquake caused extensive damage that was further exacerbated by widespread fires that swept across the wooden neighborhoods of Tokyo and Yokohama. Both cities were devastated as well as surrounding prefectures. The earthquake caused over 130 fires, some of which merged into firestorms. The most infamous was in the Hongō district, where around 38,000 people perished in an open space where they had taken refuge – heat and oxygen deprivation caused by the firestorm being principal causes.

Tokyo’s infrastructure—including roads, bridges, water supply, and railways—was either damaged or destroyed, crippling transportation and communication. Yokohama, then a major international port, was almost entirely flattened. An estimated 105,000–142,000 people were killed, with over 570,000 homes destroyed leaving more than a million people homeless. The event and its aftermath reshaped Japan’s approach to urban planning, emergency preparedness, and national resilience. 

A previous post offered a brief discussion of a complicated issue – the governance of wartime Japan. Such governance was a complicated, ritual process involving Emperor Hirohito and the Supreme War Council (“Big 6”). In the shadows of the ritual were the Lord of the Privy Seal (Kido) and other confidants of the royal family. Rather than detail the process, it is perhaps best explained by decisions around Ketsu Go.

On January 20, 1945 there was an Imperial audience in which senior Army and Navy leaders briefed the Emperor on the strategic concept for Ketsu Go. This was not a formal Gozen Kaigi (Imperial Conference), but an Imperial audience in which senior Army and Navy leaders briefed Hirohito. The principals in attendance were War Minister Anami and Army Chief Umezu – both hardliners – and Navy Chief Toyoda who at his point was supportive of the Army’s position.

It was not a detailed plan, but a strategic overview of Ketsu-Go in the context of the war: Leyte Island in the Philippines had fallen, there was no doubt that Iwo Jima and Okinawa would soon be invaded, and routine bombing of the home islands by B-29s had begun. All indications were that the southern island of Kyushu would be invaded in the late-summer to early-autumn of 1944. Most likely after the end of typhoon season which traditionally “ended” November 1st.

Ketsu-Go (“Operation Decisive”) was Japan’s final defense plan in World War II.  It outlined the defense of the Japanese home island. At this point in the war the plan is an Imperial Army-led plan with the Imperial Navy playing a limited role apart from Naval Aviation. As noted in the previous post, as from the outset of the war the Imperial Army was “in charge” – not only in the Supreme War Council but in operational planning.

The goal of Ketsu-Go was to mass Japan’s remaining troops, planes, and special attack units (kamikaze) to repel the invasion, especially on the southern island of Kyushu, expected to be the first invasion point – as it would be in the Allied plan for invasion. The hope of Ketsu-Go was to make the battle so bloody and costly for the Allies that they would lose the will to continue the invasion and offer better surrender terms than complete and absolute surrender. At stake was Kokutai, an expression that literally means “national body” or “national essence”. This is explored in greater detail in the next post, but sufficient for now, this concept was not differentiated from the Emperor and the royal household.

In Ketsu-Go there was a fundamental realization that this would not be a repeat of their 1905 naval victory at Tsushima but only a last ditch effort to achieve what was always the goal of the original Kantai Kessen – an armistice with the United States that left Japan and its early war gains intact. Ketsu-Go would run head-long into the Allied demand for unconditional surrender that had no intention of leaving Japan militarized or with any of its early war gains. The allied demand for unconditional surrender had already been decided at the Casablanca Conference two years earlier (January 1943). 

In addition there was a more fundamental issue at play: the idea of surrender. For the western soldier, surrender was not good, but it was logical. When the circumstances indicated that you’d run out of options the only “reasonable” options were retreat (live to fight another day) or simply live and place yourself at the mercy of your captor. For the Japanese soldier, surrender was the greater shame. The view was grounded in a complex mix of military indoctrination, cultural values, and fear of dishonor. Surrender was considered not only shameful but a betrayal of one’s duty to the Emperor and nation – to the Kokutai. 

This difference was clear from the beginning of the war. Consider General Wainwright’s decision to surrender the Bataan Peninsula (Philippines) at the beginning of the war. The Filipino and American troops were out of ammunition and food; further resistance meant sure death. Their Japanese captors considered them shameful cowards who had betrayed their country – and were treated as such, the Death March of Bataan giving ample evidence.

The Japanese resolve to not surrender was experienced in every land battle from Guadalcanal to Okinawa. In campaigns such as Tarawa, Biak, Kwajalein, Saipan, Tinian, Guam, Peliliu, Iwo Jima, and Okinawa fewer than 2% of the Japanese garrison was captured. The remainder fought to the death.  At the same time the casualty rates among allied ground troops in the Pacific were rising especially in comparison to the European Theater of Operations. Here are comparative casualty rates:

• D-Day Normandy France – 6-7%
• Tarawa – 20%
• Peliliu – 35%
• Iwo Jima – 37%
• Okinawa – 27%

These differences were well known to the American public.

From the high-levels of strategy to the on-the-ground reality of war, the mindset of the warring parties could not be farther apart. Ketsu-Go was not a strategy to win a battle or defend the Japanese home islands from devastation and death. It was a strategy to exact a high price of Allied casualties to avoid the shame of surrender. Ketsu-Go reflected a mindset that, if implemented, would extract an unimaginable price in human life and leave the survivors with scars for a lifetime.

Ketsu-Go was first presented to the Emperor in January 1945. In the background of the plan was the uniquely Japanese concept of kokutai.

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives.

The Japanese could intercept Allied radio traffic, but they lacked the computational resources and personnel to break complex Allied codes like Naval Cypher No. 5. Their cryptanalytic efforts were centralized and bureaucratically fragmented, lacking the scale and success of U.S. or British efforts. As a result Japan remained largely blind to Allied operational planning, especially in the Central Pacific campaigns. In addition, their intelligence analysis and interpretation – especially on a strategic level – was hindered by their rigid military culture and intense rivalry between the Army and Navy. Their military intelligence units operated as though in silos. Intelligence was often ignored or suppressed if it conflicted with existing assumptions or the wishes of senior commanders who operated on biases about the lack of a warrior spirit among allied soldiers and sailors. The senior commanders also underestimated American industrial strength, technological innovation, and the ability to sustain large-scale operations across the Pacific.

But it does not mean they were uninformed.