The Emperor's Codes

by Michael Smith

  A number of the Bletchley Park ‘Hut 7’ codebreakers had already been posted to Colombo, among them Norman Scott, and they were to play a crucial role in the sinking of one of the last big ships available to the Japanese Navy, the heavy cruiser Haguro. Scott was working on JN11, which in a sign of the drastic improvement wrought at Colombo was now solved as quickly by the British as by the Americans, if not more quickly, and had become their most important source of intelligence.

  Most of us at Bletchley Park and at Anderson knew what was needed to do our jobs, but little else. We realized that our efforts could shorten the war but we rarely knew just how. There was, however, one instance where I could see that my personal effort had directly contributed. Towards the end of May 1945 the senior translator on duty came over with a very current, but scantily readable message on JN25. He explained to me that the Japanese were anxious to get a supply convoy from Singapore to the garrison and airfield in the Andaman Islands. It was known that a Japanese cruiser of the Haguro class was involved in this relief operation. This message was expected to lay out the plans. So I buckled down to work. Including the new message, I recollect a depth of three or four on the mostly unsolved worksheet. The translator alternately phoned HQ's intelligence section with more scraps of the message and then suggested words which I could try in the still unsolved columns.

  At 8 p.m. the relief translators came on watch, but no cryptanalyst. Apparently there was a big party going on in the mess. I can remember taking a few minutes’ break in the canteen at the station for a mug of tea and a sandwich. Then it was back to the grind and slog. From 2 a.m. to 8 a.m. the designated cryptanalyst on duty was myself. However, we now began to make significant progress. By about 5 a.m. the intelligence people were no longer calling every ten minutes. I drank more tea in the comparative cool of the pre-dawn hours. Until the evening of that day, no noisy party in the mess could have disturbed my sleep after being on watch for twenty of the previous twenty-four hours.

  Some three or four days later the local press printed a naval communiqué which gave the news that a flotilla of British destroyers had sunk a Japanese cruiser in the Indian Ocean. Not long after a DSO was awarded to the flotilla commander and a DSC to one of the destroyer commanders. Over the years more details of this naval action have come to light. It seems that the four British destroyers had enjoyed sufficient lead time to practise their tactics. Contact was first made at night by radar. The destroyers were then able to spread out and approach within range of the cruiser's heavier guns from four directions simultaneously. Amid much ensuing confusion, the Haguro was finally sunk by gunfire and torpedoes.

  The sinking of the Haguro, and the contributions played by Anderson in providing intelligence on the Japanese Navy's movements and intentions during the attacks on the Philippines, Okinawa and Rangoon, led to a congratulatory telegram from Bletchley Park and a morale-boosting visit to the station from Mountbatten himself, during which the Supreme Allied Commander South-east Asia told the Royal Navy codebreakers they were worth ‘ten divisions’.

  Bletchley Park was not just sending codebreakers to Colombo to help them to improve their efforts against JN25. Peter Laslett was posted to Washington, where he worked in the OP-20-G Communication Annex on Michigan Avenue and saw no sign of the disagreements over co-operation that had soured relations at senior levels.

  The American effort was much more substantial and much better supported. But they hadn't the same experience of codebreaking as some of the people at Bletchley Park so their facility of breaking it was not really commensurate with the effort they were putting in. My main job was to explain to the Americans how we did it. I heard rumours of bad relations at a higher level, but my relationships with the people actually attacking the codes were good. I was conscious that the Americans thought the British had made a right balls of the war and, of course, conversely, we thought the Americans had. But the use of our material was of less importance to us. We were only interested in rebuilding the book. If we could get a third of the code groups in a book recovered before it was changed that was what gave us satisfaction. A half was virtually impossible, but a third was good.

  Meanwhile, back at Bletchley Park, with the war in Europe over, one of the most secret locations in the country was about to become the focus of a radio programme to be broadcast across the length and breadth of the country. The amount of musical talent congregated at Bletchley had come to the attention of the producers of a popular BBC Home Service music programme, Bernard Keeffe recalled. ‘Alec Robertson turned up in June 1945 with a BBC Outside Broadcast van and recorded a selection of our music-making for a special edition of Music Magazine. I made my first broadcast as soloist in Vaughan-Williams's Mass in G minor. The Japanese War was still on and yet, in an extraordinary breach of security, the most secret establishment in the country was introduced to the world on the Home Service on a Sunday morning.’

  The rather erudite goings-on at the British codebreaking centre were in complete contrast to events in the Far East. Bitter fighting was continuing on Okinawa and the Philippines where the Advanced Echelon of Central Bureau had now moved to San Miguel, supported by the army air codebreakers, the RAAF's 5 and 6 Wireless Units, a detachment of 4 Wireless Unit and the 111th, 125th and 126th Signal Radio Intelligence Companies.

  The rest of 4 Wireless Unit was taking part in the operations to recapture Borneo. Accompanied by the young British Army intelligence officers Tony Carson and Hugh Melinsky, they had landed on the island of Labuan, north-west of Borneo, early on 10 June, Melinsky recalled.

  At precisely eight o'clock the morning calm was shattered as every warship opened up with its big guns firing on to the Japanese coastal defences. The peaceful shore beneath its swaying palms shook and leapt, and dark columns of dirt rose and fell, to be replaced by another and yet another until the whole shore became a grey swirling mass punctuated by orange points of explosions.

  Then the assault began. The small landing-craft which had been huddling round the transport ships like chicks round a hen slowly drew away into formation heading for the shore. On the stroke of nine o'clock the barrage stopped and a few minutes later the first wave of soldiers was lost to sight in the smoke and debris of the plantations. The rattle of rifle and machine-gun fire echoed across the water of the bay as further waves of troops moved in, and soon the larger landing-ships nosed clumsily up the beach to disgorge tanks and lorries, guns and ammunition. I retired below for a drink of iced water…

  The ops tent was soon up and working, the messages started coming in, and we did our usual job of decoding and translating them and sending the results to Captain Nave in Brisbane, though now by wireless. The local battle went on for ten days, of which we were well aware because we had a battery of large guns, twenty-five pounders, firing shells over our heads against a cave where the surviving enemy were gathered. One night a hundred or so of them broke out and made their way to the beach by way of the airfield. Their officers used their swords and the men their bayonets because they had run out of ammunition, and several Australians and Americans were killed and wounded before the Japanese were finally overcome. They must have passed very near our tents.

  The operations met little resistance and by the middle of June virtually the whole of Central Bureau, including most of the elements that had so far been left behind in Brisbane, were being moved forward to San Miguel. Eric Nave was deemed to be unfit for the tropics and left in charge of a rear detachment where he continued to work on the naval air codes that were giving away the details of Japanese convoy movements.

  In a letter home to his young wife, Geoff Day described Central Bureau's arrival at its new base.

  San Miguel is only a village. The nearest town is Tarlac, some seven miles away and the capital of the province. The district around here is cultivated mainly for sugar plantations but also for the inevitable rice fields. At the moment, we are temporarily camped in a paddy field, dry fortunately, but just like a ploughed field. We had to slee
p on it for our first night, not too comfortably either, as you can imagine, but after that we were presented with canvas cots. Our washing facilities consist of dipping in water from a running stream and to take a shower one has to strip off in the open. There is no danger from enemy aircraft here but there are still quite a number of Japs around. Last week, 100 were killed in the San Miguel area. We have a range of mountains to our east and one to the west. There are still a fair number of Japs in the eastern range trying to get access to the west where they believe they can escape to the sea. Unfortunately we are in the middle and thus are subject to infiltration tactics the whole time. We have protection from the Philippine Guerrilla Army who prowl around constantly, especially at night. It pays to answer their challenge pretty quickly.

  Hugh Melinsky was sent to San Miguel from Labuan followed later by the rest of 4 Wireless Unit.

  We were on the edge of a large sugar plantation where they brewed alcohol from the sugar-cane. It was good to see ordinary people around the place again, and we were particularly glad because the Filipinos were willing to wash and iron our clothes for us at a small charge, and I felt very smart as a result. I met up again with a number of friends, including Peter Hall, who had been with 6 Wireless Unit since it arrived in the Philippines on the day after the first landings. General MacArthur was making his plans for the final invasion of Japan on the southern island of Kyushu and we were told that we were going to be the only non-American unit involved. I never did understand why his staff were so dissatisfied with the work of the equivalent American units.

  By now, the ability to read the mainline army codes captured at Okinawa and the regular ‘Tokyo Circular’ sent to Japanese military attachés in the embassies abroad was providing chilling reading. The determination with which the Japanese defences were being built up on the home islands, the surprising number of troops the Japanese High Command could still call on, the presence of several thousand aircraft that were being prepared for suicide attacks and the proven willingness of the Japanese elsewhere to fight to the last man gave the Allies pause for thought as they prepared to invade Japan.

  Since March, General Curtis LeMay had been directing a series of devastating raids on the Japanese mainland. Flying from the Marianas, 1,500 miles south of Tokyo, and escorted by fighter aircraft based on the recently captured island of Iwo Jima, the US bombers had launched a series of low-level fire-bomb attacks on Japanese cities. On the night of 9–10 March a total of 1,667 tons of incendiary bombs were dropped on Tokyo, in the most devastating single air raid ever launched. Sixteen square miles of the city's mainly wooden and paper residential districts were razed to the ground and upwards of 84,000 people, many of them women and children, killed.

  The Allies were by now aware that a sizeable faction within the Japanese Government would be prepared to sue for peace, but the Ultra signals intelligence from the mainline army and navy codes showed that, despite such horrific losses, the Japanese military remained determined to fight on.

  The only man capable of bringing the Japanese Army to heel was the Emperor himself. On 12 July the codebreakers intercepted a Purple message from the Japanese Foreign Minister Togo Shigenori to Japan's Ambassador in Moscow ordering him to pass on to the Russians an urgent plea for peace from Emperor Hirohito. The message was sent just days before the Potsdam Conference at which Stalin was to meet Churchill and Harry Truman, the new US President. ‘His Majesty the Emperor, mindful of the fact that present war daily brings greater evil and sacrifice upon peoples of all belligerent powers, desires from his heart that it may be quickly terminated,’ it said. ‘But so long as England and United States insist upon unconditional surrender in Great East Asian War, Empire has no alternative but to fight on with all its strength for honour and existence of Motherland. His Majesty is deeply reluctant to have any further blood lost among people on both sides and it is his desire, for welfare of humanity, to restore peace with all possible speed.’

  Truman was already on his way to Potsdam when Hirohito's peace approach was decoded. Allied intelligence had advised that if the Emperor ordered the Japanese armed forces to surrender they would obey but that if ‘unconditional surrender’ meant the Emperor must lose his throne and be treated as a war criminal, the Japanese would fight to the last man. As a result the Combined Chiefs of Staff had urged on their respective governments a modification of the term ‘unconditional surrender’ to make it clear that the Emperor would be allowed to stay in place.

  Four days after the Emperor's message was intercepted, the first atomic bomb was tested at a site in the New Mexico Desert. For reasons which remain inexplicable, the final declaration of the Potsdam Conference made no attempt to clarify the terms of surrender and, despite an acceptance by both America and Britain that the Emperor would have to be retained in order to control post-war Japan, no attempt was made privately to reassure the Japanese that he would not be forced to stand down. America and Britain issued an ultimatum to Japan. If there was not an immediate and unconditional surrender, it would lead to ‘the inevitable and complete destruction of the Japanese armed forces and… the utter devastation of the Japanese homeland’.

  Lacking any assurances over the future of their Emperor, the Japanese were never likely to surrender. At 8.15 on the morning of 6 August 1945, a B-29 bomber of the USAAF's 509th Composite Group dropped an atomic bomb on the south-western Japanese port of Hiroshima, flattening two-thirds of the city. Three days later a second bomb exploded over the port of Nagasaki, destroying the bulk of the city. Although the Allies put the number killed in the two attacks at around 120,000, Japanese sources have argued convincingly that it was double that number. Whatever the figure for those killed immediately, the appalling long-term effects of radiation on successive generations make it impossible to come to a final death toll. Peter Laslett recalled the events of August 1945:

  My most vivid memory of the whole war was sitting in the Annex on a hot Washington night and decoding this Japanese naval message reporting that the genshi bakudan, the atomic bomb, had been dropped on Hiroshima. The Japanese had not referred to an atomic bomb in traffic before so I believe I was the first person to decode and translate the words that night. It was a terrible shock. As far as I recall, it didn't give any casualty figure but it must have given me some sort of evidence of the devastation. The sense of disaster was very clear.

  Even before the news that the atomic bomb had been dropped on Hiroshima was officially announced, the messages arriving in Bletchley Park provided a frightening vision of what had happened, recalled Rosemary Calder. ‘I was on a day watch by myself and all this stuff came in and it was total gibberish,’ she said. ‘I didn't know the bomb had been dropped but you could tell from the disruption of all the messages that something terrible had happened. You could just feel the people standing there screaming their heads off.’

  Later messages were more specific. An army air message to the chief of staff of the General Army Air Command in Tokyo deciphered at Bletchley Park gave one of the first descriptions of the now familiar mushroom cloud associated with the atomic bomb: ‘There was a blinding flash and a violent blast – over the city centre, the flash and burst were almost simultaneous but in the vicinity of the airfield the blast came two or three seconds later – and a mass of white smoke billowing up into the air.’

  The dropping of the atomic bombs and the Soviet Union's invasion of Manchuria on 9 August led the Japanese Government to sue for peace. Only then were they informed of the precise terms of the unconditional surrender under which they would not only be allowed to keep their Emperor but were assured that the four main islands would remain part of Japan. Had such an offer been made two weeks earlier the war would almost certainly have been ended without recourse to the atomic bombs.

  On 14 August Jack Grafing, a US Navy intercept operator, was on duty at the Adelaide River interception site south of Darwin.

  I copied the first message in Japanese plain language I had ever heard. It was Emperor Hirohi
to's message to his troops to lay down their arms. After the Japanese surrender we closed the station at Adelaide River. I heard a long time later that our group was a key link in the information-gathering, and I do recall receiving some kind of a unit citation after I had returned home. At that time everything was still top secret, and since I was out of the navy, they could not tell me much about what it was for.

  Around the world, the codebreakers and intercept operators working on the ‘Japanese problem’ had become redundant. Julie Lydekker was a WAAF who had been working on the index in the Japanese air section at Bletchley Park and had been sent to Washington to show the Americans how to set up a similar operation.

  Washington was another world after the austerity and grind of Britain in 1945. For the first time in four years there was no weekend work, but wonderful opportunities for sightseeing, concerts and marvellous food. I had never seen one-inch fillet steaks and real cream ices like the ones that were normal fare there. Nothing could have been more of a contrast to Bletchley and its one cinema, tatty café and local pubs. On VJ Day Washington was vibrating with excitement, tempered with relief that the war with Japan was over. Everyone with a car converged on the White House with their hands firmly pressed on their horns, making an unbelievable cacophony which went on all day and was followed in the evening by a stunning firework display.

  Olive Humble was on leave from the Hut 7 naval section when Japan surrendered.

  I came back to Bletchley Park two days later to find all the civilians had shipped out. I was sent to the fearsome Commander Thatcher, who lectured me again about keeping my mouth shut for all time, had to re-sign the Official Secrets Act, and was threatened with the thirty years and/or firing squad if I went off the straight and narrow. I was then given a month's salary, a total of £3, plus or minus a few shillings, and I said farewell to the navy, and to Major M, who gave me a glowing reference, including words like ‘National Importance’. Then I received the Foreign Office one, which was even better: ‘employed on important and highly specialized work of a secret nature. The Official Secrets Act precludes any information in connection with these duties.’ Heady stuff, even better than navy cocoa!