Category Archives: Japan

Last Naval Battle of World War II?

From When the Shooting Stopped: August 1945, by Barrett Tillman (Osprey, 2022), Kindle pp. 208-210:

Meanwhile at sea, probably the last naval engagement of the war was fought off the China coast. On the morning of August 21 two sailing junks with American-Chinese crews were en route from Haimen to Shanghai. They were attached to the clandestine Sino-American Cooperative Organization, supporting guerrilla operations in Asia.

Lookouts sighted a large junk ahead; then the stranger came about, unmasking its armament, and opened fire.

Unknown to the two U.S. skippers – Navy Lieutenant Livingston Swentzel, Jr. and Marine First Lieutenant Stuart L. Pittman – their black-painted rival was a potent adversary. It carried a 75mm-pack howitzer, six machine guns, and more than 100 rifles for the 83 Japanese soldiers on board. Swentzel was a 35-year-old New Yorker with a degree from William and Mary whose excellent academic education ill prepared him for the situation.

The enemy’s first round was eerily accurate, severing Swentzel’s foremast to the consternation of most of his crew. Four Chinese were killed or wounded and the rudder damaged. However, Swentzel radioed Pittman, who coordinated the response. And in a brief moment of recalled glory from the age of sail, Swentzel hoisted the Stars and Stripes before returning fire.

Closing to 100 yards, the Yanks opened up with their heavy weapons – two bazookas intended for antitank action rather than naval warfare. One of Pittman’s sailors took two rounds to get the range, then knocked out the Japanese cannon, but both sides retained automatic weapons. After holing the enemy vessel, Swentzel directed Pittman alongside the Japanese and gave an order that John Paul Jones would have approved 170 years before: “Prepare to board!”

Hull to hull, Pittman’s half of the seven Americans and 20 Chinese led their attack with a hail of hand grenades to kill or disperse the superior Japanese numbers. With the Marine in the lead, a brief, violent skirmish subdued most of the remaining enemy, driving others below decks. More grenades followed down the hatches, forcing the survivors to surrender.

After 45 minutes the issue was settled, climaxing when the opposing skippers clashed hand to hand, with Pittman victorious. Before he expired, the Japanese officer told the Chinese that he had thought the junks were pirates. Americans and Chinese sorted the Japanese casualties, reckoned at 44 dead and 35 wounded. The Allies lost four dead and six injured. Swentzel and Pittman reversed helm for Haimen, and delivered their prize and prisoners to the Chinese before proceeding to Shanghai. Both skippers received Navy Crosses for their utterly unique action.

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U.S & Japan Negotiate in German, 1945

From When the Shooting Stopped: August 1945, by Barrett Tillman (Osprey, 2022), Kindle pp. 206-207:

Thousands of American servicemen crowded both sides of the landing strip, watching the historic moment. Military police could barely restrain them from swarming the two planes, seeking a closer look or perhaps souvenirs.

With minimal fanfare the Japanese disembarked from the two bombers and approached MacArthur’s personal transport, the gleaming aluminum C-54 dubbed Bataan in memory of his Philippine service. Leading the delegation was Lieutenant General Torashiro Kawabe, sporting a long sword and spurs. Besides Kawabe and a major general were six other army officers including two interpreters, a rear admiral with four other navy men, and three civilians. The senior diplomat present, Katzuo Okazaki, had been a runner in the 1924 Paris Olympics.

The Douglas Skymaster loaded its human cargo and headed 920 miles south.

In Manila, skirting angry Filipino crowds, the entourage motored to an apartment building that, unlike City Hall, had survived the liberation relatively intact. The Japanese received a pointed message from the conqueror: they were not present to negotiate. Their purpose was simply to learn the specifics as to the terms of surrender and protocol of the impending ceremony. Keeping himself remote from the discussion as befitted a budding emperor, MacArthur allowed his intelligence chief, Major General Charles Willoughby, to conduct much of the meeting. Willoughby asked Lieutenant General Kawabe, vice chief of the Imperial Army, what language they should speak, to which the multi-lingual general replied, “German.” That suited Willoughby – he had emigrated from Germany as a child in 1910.

The details were thrashed out with minimal problems. MacArthur’s staff intended to land at Atsugi in four days, to which the Japanese objected for practical reasons. It was a kamikaze base and “a hotbed of revolt against the cease-fire.”

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USSR vs. Japan, 1945

From When the Shooting Stopped: August 1945, by Barrett Tillman (Osprey, 2022), Kindle pp. 118-120:

The Far East blitz represented the acme of Russian military operations in the Great Patriotic War. An American historian properly described the Manchurian offensive as “a post graduate exercise for Soviet forces, the culmination of a rigorous quality education in combat begun in Western Russia in June 1941.”

Red Army losses in the 25-day campaign were 35,000 overall with 11,000 killed, while naval components added 1,400 casualties. In the Kremlin’s hard-eyed accounting, it was nearly a bloodless conquest of an immense, productive area.

Overall in the Far East, the Soviets captured 594,000 Japanese troops, including 143 generals and 20,000 wounded. Almost certainly the astonishing bag of general officers would not have occurred a month before, suicide being the preference.

Postwar Western figures placed Japanese losses at 674,000 including 84,000 dead. American intelligence estimated that the Soviets captured 2.7 million Japanese, two thirds of them civilians. Eventually some 2.3 million were repatriated to Japan, with 254,000 known dead and 93,000 presumed dead.

Of some 220,000 Japanese farmers established in Manchuria, about 70 percent reportedly perished, including perhaps 80,000 in the severe winter of 1945–46. More than 10,000 were thought killed by outraged Chinese, or had committed suicide. Presumably the surviving 140,000 eventually returned to Japan.

The Russians dismantled much of Manchuria’s industrial plant within three weeks of the war’s end, ceding the territory to the Communist Chinese. Thus, without realizing it, Moscow had set the stage for the next war, only five years downstream.

* * *

In the vacuum attending Japan’s defeat, Soviet forces entered Korea in mid-August, advancing southward to the designated 38th Parallel that would mark the boundary between Soviet and American occupation zones. The Russians lost little time exploiting their control over the area, especially since many Koreans welcomed an end to 40 years of Japanese rule.

In the north, Korea already possessed two military organizations: Kim Il-sung’s guerrilla force and the Korean Volunteer Army headquartered in China. The Soviets established headquarters at Pyongyang and almost immediately founded an air force academy.

Meanwhile, the Americans – thin on the ground in the south – planned to retain many Japanese for continuity of government. The reaction among South Koreans was stridently vocal, leading to a quick reversal by the U.S. administrators. However, frequently they consulted their Japanese counterparts, who naturally recommended Koreans who had cooperated with Tokyo. Two distinct Koreas were emerging and battle lines, however unwittingly, were already drawn for the coming Cold War.

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Planning the Invasion of Japan, 1943-45

From When the Shooting Stopped: August 1945, by Barrett Tillman (Osprey, 2022), Kindle pp. 57-58:

While naval air combat carried on unabated, groundwork continued for the ultimate objective, an invasion of Japan. The overall Allied invasion plan, aptly titled Downfall, originally had been discussed at the 1943 Casablanca Conference, calling for a two-phase assault: Operation Olympic against the southern island of Kyushu in November, and Operation Coronet on the main island of Honshu the following March. Both would be enormous undertakings: Olympic involved about 350,000 men in combat units plus a further 125,000 support personnel; Coronet more than half a million. In comparison, the initial D-Day landings in Normandy committed approximately 150,000 Allied troops.

Building the force to invade Japan required a gargantuan combination of planning, coordination, and logistics. Previously, Admiral Ernest King, chief of naval operations, had reportedly quipped, “I don’t know what the hell this ‘logistics’ is that General Marshall is always talking about, but I want some of it.” In fact, the Navy was the essential factor in transferring troops from Europe and the United States. Nearly everything without wings had to go by sea, and so did many aircraft.

By August 1945 at least four armored divisions were based in the continental United States, with two or more infantry divisions preparing to deploy west.

The Army also intended to redeploy more than 395,000 men directly from Europe, all between September and December. They included units dedicated to Olympic or Coronet, representing Army Ground Forces, Air Forces, and Service Forces.

At the same time planning proceeded for 477,000 soldiers and airmen to round out the Coronet order of battle, moving from Europe through “ConUS” to the Pacific between September 1945 and April 1946. That amounted to a total of nearly 875,000 personnel moving halfway around the world in eight months. And that did not count Army, Navy, and Marine Corps personnel already in the Pacific. Nor did the redeployment figures include Doolittle’s Eighth Air Force units transitioning to B-29s with 102,000 aircrew and maintainers, either from Europe or originating in the States. The transport burden was further increased by 75,000 European Theater hospital patients beginning in late 1944.

Despite the clear logistical nightmare of such an undertaking, there was one clear advantage to the Allies. Throughout the war they had consistently outperformed the Axis in the crucial realm of supply, which was far more than simply building “stuff.” King’s quip concealed the Anglo-American mastery of the logistical trilogy: planning, production, and distribution. British historian Richard Overy properly noted that the American “tooth to tail” ratio of warfighters to rear-echelon and support personnel ran 18 to one; Japan operated at a support to combat ratio of a mere one to one.

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ULTRA vs. IJN Submarine I-29, 1944

From Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations Against Japan, 1941-45 (The Secret War), by John Winton (Sapere Books, 2022), Kindle pp. 294-296:

ULTRA betrayed not only convoys but single blockade runners. The fate of I-29 was a perfect ULTRA coup. I-29, named Matsu, was the submarine which rendezvoused with a German U-boat off Madagascar in April, 1943, embarked Subhas Chandra Bose, the leader of the movement for Indian independence and self-styled C-in-C of the Indian National Army, and took him to Penang. I-29 (Cdr T. Kinashi) left Penang, bound for Europe, early in November, 1943, and sailed from Lorient, bound for Japan, on 16 April, 1944. Among the passengers were four German technicians and thirteen Japanese Army, Navy and civilian personnel. The cargo included German anti-submarine counter-measure equipment, acoustic and magnetic torpedoes, radar apparatus, plans for the latest high-submerged-speed submarines, and influenza virus.

I-29’s passage was traced through intercepted signals from Berlin, and a Singapore broadcast in diplomatic code, addressed to I-29 only on 3 July, indicated its presence in the Indian Ocean. An ULTRA from Anderson on it July read: ‘Friendly sub [identified as probably I-29] scheduled to pass through Sunda Strait on morning of 12 July, and arrive at eastern entrance to Singapore at 1200 on 14th.’ It was later confirmed by ULTRA that I-29 had indeed arrived that day.

On 17 July, 1944, a decrypted message from Berlin to Tokyo listed I-29’s cargo in detail: five ‘special weapons’, various radar apparatus, 20 Enigma coding machines, ordnance parts, rocket-type launching apparatus, bomb sight plans, pressure cabin parts and plans, parts of a British Mosquito plane, and atabrine ampoules and tablets. Two days later, in a decrypted message, Berlin congratulated Tokyo: ‘It is indeed gratifying to learn that the MATSU has arrived safely at Singapore with her passengers and cargo. We pray for her safe voyage to Japan.’

But on 20 July Kinashi broadcast a fatal signal giving full details of his route to Japan: leaving Singapore at 1500 on the 22nd, arriving Kure at 1000 on 30 July, and giving his noon position for the 26th as the Balintang Channel [between Formosa and Luzon]. CincPac’s Bulletin for 24 July read: ‘I-29 recently arrived Singapore from Europe carrying samples and plans of many recent German developments in fields of radar, communications, gunnery, aeronautics and medicine. Left Singapore 22 July en route Kure. Believe very important cargo very likely still aboard. Will pass through posit 15 N., 117 E., at 251400 and through Balintang Channel at 261200, speed 17 arriving western channel of Bungo Channel at 291000.’

On 25 July I-29 signalled that a surfaced enemy submarine had been sighted (possibly the ‘cover story’) and gave the position, about 300 miles west of Manila. On the 26th Sawfish (Cdr A. B. Banister, leader of ‘Banister’s Beagles’) signalled: ‘He did not pass. At 0755Z [1655 local time] in posit 20-12 N., 121-55 E. [Balintang Channel] put three fish into Nip sub which disintegrated in a cloud of smoke and fire.’

On 7 August a mournful Tokyo broadcast to Berlin was intercepted: ‘All her passengers had proceeded to Tokyo from Singapore by plane, but her cargo had been left aboard. Though it is indeed regrettable, we can no longer hope for her safety. Despite the fact that we received, through your great efforts and the understanding cooperation of the Germans, many articles which were to strengthen the nation’s capacity to prosecute the war, our inability to utilize them owing to the loss of the ill-fated ship is truly unfortunate and will have a great effect throughout the Imperial Army and Navy.’

I’m pleased to see that Cdr. T. Kinashi’s name is spelled consistently in this book, and that this remarkable naval officer has a detailed article in English Wikipedia (linked above). Several other Japanese names are handled quite sloppily. For instance, the IJN destroyer Kuroshio (‘Black Current’) is consistently misspelled Kurishoyo six times on pp. 276-278, and Lt. Gen. Kuribayashi, the Japanese Army commander on Iwo Jima, is transliterated correctly on p. 304, then misspelled as Kuribayasha twice on p. 306. (The Hawaiian place name Wahiawa is also misspelled as Wahaiwa on p. 158.)

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Destroying Truk, February 1944

From Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations Against Japan, 1941-45 (The Secret War), by John Winton (Sapere Books, 2022), Kindle pp. 225-227:

Known as the ‘Gibraltar of the Pacific’, Truk was in fact not nearly as strongly defended as legend had it, but it was the best fleet anchorage anywhere in the Japanese mandated islands and had been the regular base for the Combined Fleet since July, 1942.

Truk’s geographical layout, of scattered volcanic islands inside a triangular-shaped coral reef, made it virtually impregnable to surface attack from outside its perimeter. But it was open to the air. After the same FRUPAC analysis of air search patterns from Truk as from Kwajalein, a powerful task force including six fleet and four light carriers in three groups under Mitscher (who had relieved Pownall in January) made a fast and undetected run towards Truk in the night of 16/17 February, 1944, to carry out Operation HAILSTONE.

Spruance himself was present, flying his flag in the battleship New Jersey (the fleet commander had also been present during the Marshalls landings, ready to take over command if the Combined Fleet sallied out). But there was no chance of that. Truk was just within bombing range of Kwajalein and Bougainville, and its supply route from the Empire was constantly beset by US submarines. Thus, Truk was no longer the safe base it had once been.

Photo-reconnaissance of Truk on 4 February showed plenty of targets, but the same reconnaissance flight had given the game away to Admiral Koga, who sent most of his warships to Palau and went back to Japan himself in the giant battleship Musashi.

The last cruiser, Agano, left Truk on 16 February and was torpedoed and sunk by the submarine Skate the next day. But the fleet auxiliaries, the oilers, seaplane carriers, submarine tenders and many Marus of the support force were due to leave later and were still in Truk when the first fighter sweep, launched from a point 90 miles north of Truk before dawn on 17 February, caught the defenders by surprise.

Seventy-two fighters followed by eighteen Avengers with incendiaries found some fifty merchant ships in the harbour and 365 aircraft ranged on the airfields. The strike put all but a hundred of the aircraft out of action. The carriers then mounted more or less continuous strikes of fighters, bombers and torpedo-bombers to work over the airstrips and attack shipping. That evening the Japanese made their only reply, a torpedo attack by Kates who scored a hit on the carrier Intrepid (a somewhat unlucky ship, nicknamed ‘The Evil I’), putting her out of action for some months.

In the meantime Spruance in New Jersey with another battleship, Iowa, two heavy cruisers, four destroyers and the light carrier Cowpens to give air cover, made one anti-clockwise sweep round Truk to catch any would-be escapers. They sank the light cruiser and Sixth Fleet submarine flagship Katori and the destroyer Maikaze.

That night a strike of Avengers, specially equipped and trained for night bombing, attacked shipping in the lagoon. It was the first time in the war such a raid had been made and it was a signal success: one-third of the total tonnage destroyed at Truk was sunk by these Avengers.

Strikes resumed the next day, 18 February. Everything that moved or floated had now been sunk or strafed and the aircraft turned their attention to fixed fittings — hangars, fuel tanks, storage dumps, buildings and vehicles. When the carriers retired at noon their aircraft had flown 1,250 sorties, dropped 400 tons of bombs and torpedoes on shipping and 94 tons on airfields and shore installations. They had sunk the cruiser Naka, auxiliary cruisers Aikoku Maru and Kiyosumi Maru, destroyers Oite, Fumizuki and Tachikaze, the armed merchant cruiser Akagi Maru, two submarine tenders, an aircraft ferry, six tankers and seventeen other ships — a total of about 200,000 tons. This was a crushing blow to the Japanese Navy. The loss of so many fleet supply and support vessels was as grave an operational defeat as the loss of capital ships. Truk was never the same again.

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U.S. vs. Japanese Submarine Warfare

From Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations Against Japan, 1941-45 (The Secret War), by John Winton (Sapere Books, 2022), Kindle pp. 190-193:

‘PRESS home all attacks,’ wrote Rear Admiral James Fife USN, Commander Submarines South-West Pacific, in his standing orders. ‘Pursue relentlessly, remembering that the mission is to destroy every possible enemy ship. Do not let cripples escape or leave them to sink — make sure that they do sink.’

The American submariners in the Far East, very ably assisted by the British and the Dutch, put Admiral Fife’s orders faithfully into effect and achieved devastating results. By VJ Day, 1945, Allied submarines in the Far East were actually running out of targets. By that time, although submarines still constituted only 2 per cent of the American war effort on the Pacific, American submarines had sunk two-thirds of the total Japanese merchant ship tonnage sunk during the war, and had also sunk one out of every three of the Japanese warships sunk.

The United States and the Imperial Japanese Navies were roughly equal in submarine strength in the Pacific at the outset of the war. Neither navy had had any operational experience of submarines in the First World War. Both had prepared for submarine warfare on a long-range scale, and primarily for use against enemy warships. The crucial difference in the Second World War lay in the US Navy’s technological advances, its readiness to profit by tactical experience, and its proper strategic deployment of its submarines. In all three areas the Americans were superior.

The one advantage the Japanese submarines had was the quality of their formidable 40-knot, oxygen-powered, longer ranged torpedoes, with twice the explosive charge of the American torpedoes. American torpedoes were frequently defective and, incredibly, it was nearly two years before the US Navy established the causes of the defects and remedied them. Under operational patrol conditions American torpedoes nearly always ran eight to ten feet below their proper depth, so that their magnetic detonators, designed to be activated by the target ship’s metal hull, failed to work properly. Similarly, the contact detonators only worked best after an oblique impact, thus, ironically, penalizing the very submarine captains who aimed best and hit their targets broadside on.

Design faults were compounded by bureaucratic obstruction: shorebound officers and bureaucrats continued to insist that the whole fault lay with incompetent submarine captains who could not aim properly, and refused to believe submarine captains who said they had heard their torpedoes hitting the target and failing to explode.

For the first months of the war Japanese submarines had considerable success in sinking Allied warships, especially in ‘Torpedo Junction’ in the summer of 1942. But the fatal Japanese tendency to indulge in non-profitable peripheral activities soon began to drain away their submarine patrol strength.

The Japanese diverted their submarines to carry midget submarines, to no tactical purpose, or to act as communication links, or to wait at rendezvous to refuel flying-boats, or to carry out unimportant surface bombardments, which had no more than pinprick nuisance value, of Midway, or Canton Island or Johnston Island, or (in 1942) the coasts of Vancouver and Oregon.

The largest Japanese submarines carried aircraft — requiring an hour after surfacing to assemble and launch — which they transported thousands of miles for valueless reconnaissance flights. One submarine, I-25, launched her aircraft loaded with incendiaries with the serious intention of setting light to the forests of North America. As the war progressed more and more Japanese submarines were taken off patrols and used to carry men, ammunition and food to beleaguered Japanese island garrisons bypassed and left to ‘wither on the vine’ by the Allied advance.

Unquestionably the best strategic use the Japanese could have made of their submarines would have been to make a determined effort to cut the supply lines from Pearl Harbor to Micronesia and Australia. They made no such effort. There was never any submarine war in the Pacific remotely comparable with the struggle against the Atlantic U-boat. The US Navy began by escorting their ships in convoys in the Pacific, but by the end of 1943 there was so little enemy submarine activity that single ships were steaming across the Pacific unescorted.

To misuse of submarines in exotic sideshows the Japanese Navy added an almost complete failure to safeguard their own surface ships against submarines. The Japanese were obsessed by the idea of an ‘offensive’ war. Like the British in the First World War, they regarded convoys as ‘defensive’ and therefore somehow demeaning and unworthy of a warrior nation. Convoy did not appeal to the Samurai spirit.

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Growth of U.S. Intelligence Staff, WW2

From Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations Against Japan, 1941-45 (The Secret War), by John Winton (Sapere Books, 2022), Kindle pp. 182-183:

Radio intelligence had also improved (although ‘Joe’ Rochefort had left Pearl Harbor in October, 1942, the victim of Washington intrigues). The Allies had begun to realize the full potential of communications intelligence. ‘In my opinion, the value of Radio Intelligence has been demonstrated to the extent that we can never again afford to neglect it as we did before the war,’ said Commander (later Rear Admiral) Joseph N. Wenger, a member of OP-20-G, in a lecture on ‘Future Co-operation between Army and Navy’ on 1 June, 1943. ‘Furthermore, the difficulties of obtaining Intelligence have increased so greatly that we shall have to maintain an organization constantly at work on high-speed electronic equipment if we are to be prepared for any future wars. The equipment necessary to obtain Radio Intelligence is growing so complicated that we cannot wait until war comes to provide it. Certainly we cannot afford to risk another Pearl Harbor.’

By 1943 the Allies were also coming to realize the scale of resources needed for communications intelligence. For instance, the number of personnel involved, both US Navy and Army — 300 in 1939 — had risen to 37,000 by the end of the war in 1945. There was an enormous expansion, in the United States and in the United Kingdom, in courses to train large numbers of people, many of them university students, to speak or read Japanese; classicists and students in dead languages usually learned to read Japanese, while modern language students learned to speak it.

Techniques had improved in every respect of intelligence, from the interrogation of prisoners-of-war to the evaluation of aerial reconnaissance photographs (colour-blind men and women were recruited because their disability enabled them to ‘see through’ camouflage).

By 1943 the Allies began to sense they were really winning the radio intelligence war against the Japanese. As more codes were decrypted, over longer periods, the cryptanalysts believed they were at last beginning to feel their way into the Japanese mind. As the Japanese suffered defeats on land and retreated, there were more opportunities to capture documents, such as diaries, operational orders and, as from [beached submarine] I-1, actual code books.

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ULTRA Protocols in the Pacific

From Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations Against Japan, 1941-45 (The Secret War), by John Winton (Sapere Books, 2022), Kindle pp. 16-18:

As the war went on, the flow of ULTRA swelled like some great tidal wave, giving accurate and timely information on every aspect of the Japanese war effort, from the strategic to the domestic — not only Japanese war intentions, but individual ships’ machinery defects and junior officers’ promotions. The number of signals involved was enormous: the National Archives and Research Administration (NARA) in Washington DC has 290,908 decrypts of Japanese Navy signals on file, as well as many more thousands of naval attaché signal decrypts, intelligence summaries and daily digests.

ULTRA provided information broadly in four main categories. There was information of critical operational value, such as convoy sailings, warship movements, impending attacks, tactics and battle orders for on-going operations, which was directly applicable to current operations and provided in time for action to be taken on it. There was information of strategic value, such as intelligence of future operations, supplies, reserves, reinforcements and current strategy; on orders of battle, including the strengths, equipment and disposition of ships, aircraft and troops; and on Japanese intelligence, such as the results of Japanese spy activity, interrogations of Allied prisoners-of-war, captures of Allied documents, and the Japanese’ own traffic analysis, reconnaissance, and interceptions and decrypts of Allied signals.

Special arrangements were made for handling ULTRA. It was revealed only to certain Flag and Senior Officers and selected members of their staffs who had been ‘indoctrinated’ into the secret. When Arleigh (‘Thirty-one Knot’) Burke was Chief of Staff to Admiral Mitscher in the carrier Lexington in 1944, he was at first curious and finally angered by the mysterious behaviour of a junior naval reserve Lt (jg) who, alone of everyone on board, was allowed private and privileged access to the Admiral. Burke would see the two talking in low voices on the wing of the Admiral’s bridge, or sometimes withdrawing into the privacy of the Admiral’s sea cabin.

The officer was Charles Sims, Mitscher’s ULTRA intelligence officer, a Japanese language specialist trained in codebreaking, who gave Mitscher highly classified intelligence available through ULTRA. Burke himself was eventually admitted into the ULTRA secret, despite Sims’ protests, but not until special permission had been sought from CincPac.

The US Navy, unlike the Royal Navy, permitted the use of the word ULTRA in the text of signals. They regularly used some phrase such as ‘This is ULTRA’, but not habitually at the beginning of a signal, which would render it vulnerable to cryptanalytical attack, but always somewhere in the body of the text.

When information from an ULTRA source was passed on in another signal, that signal had to be paraphrased and so worded that, if captured or intercepted by the enemy, any reference to enemy intelligence could not be traced back to ULTRA. Any reference to the name of an enemy ship was to be avoided and any positions taken from an ULTRA signal had to be given in a different way.

ULTRA was so powerful a weapon that it often could not be used. Much of the information it provided could not be acted upon. Too many U-boats sunk at their remote fuelling rendezvous, for instance, would arouse enemy suspicions and imperil the ULTRA secret. Any operation undertaken as a result of ULTRA therefore had to have a ‘cover story’ — some corroboration from another source, such as naval or air reconnaissance, to account for the presence of Allied forces on the scene and at the time of the action. It was very easy, through an excess of zeal, especially in the Pacific, to make mistakes over this vital requirement.

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Sources of (Mis)information After Pearl Harbor

From Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations Against Japan, 1941-45 (The Secret War), by John Winton (Sapere Books, 2022), Kindle pp. 11-14:

In the first forty-eight hours after Pearl Harbor the CIC [Commander in Chief] had a flood of misinformation which left them ever afterwards with a healthy mistrust of ‘eyewitness’ accounts, not only from excited civilians but also from experienced Service personnel, both Allied and enemy. Japanese parachute troops were reported to have landed and to be engaged in a fierce pitched battle with US Marines. The uniforms worn by these mythical Japanese were described in the most minute sartorial detail. Strange vessels were reported arriving offshore, a large enemy fleet had been seen south of the islands and at least one Direction/Finding bearing (later judged to be ambiguous and inconclusive) was obtained. One officer sighted a dirigible over Honolulu, two degrees to the right of the moon and three degrees below it. To make matters more confusing, there were seemingly improbable reports of submarines in Pearl Harbor — but Japanese submarines did indeed take part in the attack.

In the earliest, defensive, stages of the war in the Central Pacific, radio intelligence was not just the most important source of intelligence; it was, for all practical purposes, the only source. There were no photographs of enemy-held positions. There were very few captured enemy documents and even fewer enemy prisoners-of-war. Apart from the Solomons and New Britain, spies and coast-watchers supplied no important intelligence.

Radio Intelligence embraced the interception and exploitation of all enemy radio transmissions which might yield intelligence, including the decryption of coded enemy messages; direction finding (D/F); navigational beacons and aids; enemy radar and infra-red transmissions; traffic analysis, which was the study of communications networks and the procedures, signals, callsigns and plain language messages passing over them; the monitoring of enemy radio broadcasts to the civilian population; and such refinements as the study of the types and peculiarities of particular transmitters and of the idiosyncratic morse characteristics of individual operators.

Fortunately for the Allies, distances in the Pacific were vast — by 1942 the perimeter of the area Japan had conquered was between 3000 and 4000 miles from Tokyo and overland or undersea communications, such as cable, telephones and telex, were scarce or non-existent. Thus the Imperial Japanese Navy routinely generated a huge amount of radio traffic. Again because of the distances involved, much of it was transmitted by High Frequency which was detectable at long ranges by a ring of listening stations down the west coast of the United States, in the Aleutians and Australia and, before the war, at Cavite, Guam, Shanghai and Peking.

The most valuable radio intelligence was obtained from the interception and decryption of encoded or encyphered enemy messages. The Japanese themselves regarded their language as a sacred mystery, not to be vouchsafed to outsiders. Japanese hearing for the first time a Westerner speak their language were known to shake their heads dis-believingly. Such a thing was not possible; they must be dreaming.

Learning to speak or read Japanese was in itself a formidable challenge to western minds. To unravel Japanese in code would seem a virtually impossible mental obstacle. In fact, many Allied cryptanalysts found that decyphering Japanese was a matter of persistence, of ‘quantity and time rather than difficulty’. It was, if anything, tedious rather than difficult.

That is not to say that the task was easy. Whereas the Germans used versions of the Enigma machine for encyphering virtually all Kriegsmarine, Wehrmacht, Luftwaffe, SS, police and diplomatic signal traffic, the Japanese used many different crypto systems. An operational history of Japanese naval communications from December, 1941–August, 1945, compiled under Allied direction by former Japanese officers who had served during the war, lists three naval code books for strategic and administrative use; six naval code books, a joint Army-Navy code book and a Combined Fleet special code book, for tactical use; for intelligence, an overseas secret telegraph code book, two more naval code books, and five variations of a code distributed to naval officers appointed pre-war as intelligence agents stationed in Europe, the Americas and all over the Far East, and a ‘New Code Book’ for naval officers stationed on the west coast of the USA; five code books for communications with service branches outside the Japanese Navy, such as merchant ships over 1,000 tons and fishing vessels, and a standard code book used by the Navy, Army and Foreign Ministries, distributed to diplomatic officials stationed in East Asia and principal Navy and Army headquarters. There were also other publications such as books of abbreviations, address codes and call signs, and books of visual signals.

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