Precis of  “The Eavesdroppers”

I'd like to share with you a part of the story of Signals Intelligence — Sigint — in particular that part played by the RAAF against Japanese communications during WW II. The basis is this book, The Eavesdroppers, by Jack Bleakley which was published in 1991 and which contains a Foreword by the then Chief of the Air Staff, Air Marshal Ray Funnell which I will read.

Even now, after almost fifty years, few people in Australia are aware of the vital contribution made to the Allied war effort against Japan by the RAAF components of the Allied signals intelligence organizations. 

In the Pacific, signals intelligence provided the Allies with information of almost every Japanese move including the dates and locations of landings, troops to be used and details of the escorting forces.

Throughout the South West Pacific area, particularly at Darwin and the various New Guinea bases, signals intelligence provided innumerable air raid warnings and a constant flow of tactical air intelligence. This resulted in successful Allied interceptions, on the one hand, and the destruction of enemy aircraft on the ground, on the other.

A graphic illustration of the value of signals intelligence during this period is that, over four months in mid-1943, it allowed the allies to trace all movements of the Japanese Army Airforce from Japan and rear bases into the airfields of northern New Guinea. Full details of types, numbers and the airfields of destination were supplied. In a three-day period of raids by the US Air Force, this large enemy force of nearly 400 planes was virtually annihilated without having been used.

Central to this was the contribution made by the RAAF Wireless Units, and in particular the skilled and dedicated operators whose main duty was the collection, in forward operational areas, of the material required for analysis and reporting by the signals intelligence organization.

Of paramount importance to the success of the RAAF operations was the maintenance of total secrecy. That so little is known even today is an impressive testimonial to the loyalty and dedication of all those involved in the organization. For these many years they have kept those secrets. Now their story can be told.

Obviously the RAN and Australian Army were also involved in Sigint but the author does not cover those services.

Australia's involvement in Sigint evaded publicity until 1972 when the role of our Defence Signals Division, DSD, was exposed by a former employee of the giant US electronic intelligence organisation, the National Security Agency, in an article in the American journal Ramparts.

The Preface to this book acknowledges the assistance, help and encouragement given by DSD and its Director to the author. The silly part of Sigint is that every country that can will be attempting to intercept others communications, because those communications contain intent and record factual occurrences. I know there may be people here who have had access to Sigint end-product and there may be some who were actively engaged in that activity.

Some will be remembering the day they signed the document which stated that their knowledge of Sigint would not be revealed because it was covered by the Crimes Act and the Official Secrets Act.

The Eavesdroppers is primarily the story of those who intercepted the Japanese traffic but for the system to work requires quite a few other practitioners: cryptoanalysts are needed; foreign language speakers are essential; traffic analysts play an important part; technicians keep the systems working; reporters separate and process the wheat and the chaff; direction-finding can be involved and perhaps radio-fingerprinting, quite a few people make the operation work.

Jack Bleakley begins in the Preface to his book with some basics:

• RAAF Sigint began in a very small way, became integrated with General MacArthur's intelligence system, thence with the Central Bureau in Melbourne which linked to the greatly expanded Allied and U.S. Intelligence Service;

• Despite Australia's outstanding contribution to SWPA Sigint, you will look in vain for any mention of Australian units in any of the Australian war histories. One outstanding example and decisive moment in history was the operation when 17 USAF P38's fitted with long range fuel tanks intercepted Admiral Yamamoto's `Betty' bomber at the southern tip of Bougainville and shot it down. Yamamato had been the architect of the Pearl Harbour attack. The Eavesdroppers attributes interception of Yamamoto's flight plan to an RAAF operator at Townsville [p. 95/96]. Other books credit Americans with the intercept and of course, there could have been more than one interceptor involved;

• Sigint is a sensitive activity as are the names of those involved and the fruits of their labours; and

• Distribution of Sigint [ULTRA] material is on a strict need-to-know basis with extreme protective security measures being applied.

Bleakley writes of the USN forward intercept and code breaking group in the Philippines in 1941 and of General MacArthur's small, independent army intercept group at his Manila HQ, who were intercepting Japanese air-ground traffic. MacArthur placed great reliance on Sigint and valued its personnel.

Australia's involvement with Sigint began in 1921 when Lt. T.E. Nave RAN was attached to the British embassy in Tokyo to learn Japanese. He knew International Morse code, studied the Japanese kana Morse and taught himself the Japanese kata kana phonetic syllabary.

From 1937 to 1939 Paymaster Commander (P/Cdr) Nave was based in Hong Kong with the RN as an interceptor and cryptographer. In 1939 he was with the British Far East Combined Intelligence Bureau at Singapore and returned to Melbourne in May 1940 as an acknowledged authority and expert, to establish a "Special Intelligence" organisation for the RAN.

The RAN had established a small Sigint and D/F setup in Darwin (Coonawarra) Canberra (Harman) and Melbourne when Nave returned home.

The Australian government approved the setting up of our first intercept and cryptographic organisation in 1941. It had sought British "approval" in April 1940, which took until October for Britain to respond, and shows how unimportant Australia and the Pacific were to Britain at that time. It hardly took six months, even in wartime, for Britain to agree to Australia doing something they were doing in Europe, even if we had to seek expert support from Britain to do so.

In mid 1941 the Defence Committee confirmed the need to train Australian Defence Force personnel to intercept Japanese military traffic. The first seven RAAF and two Army radio operators were selected to learn Japanese Morse code and they began their training in July of that year.

All Sigint personnel in the Pacific War faced two enormous problems not encountered in Europe. These were, firstly, the complexities of the comparatively unknown Japanese language and secondly, the fact that the Japanese had devised their own form of Morse code known as the kana code for their naval and military operational messages. The Kana Morse signals were based on the 46 basic phonetic sounds in Japanese [plus 25 other sound changes] of the Japanese language, using their kata kana syllabary (p. 8).

The huge task for Allied intercept operators was to learn the 71 kana Morse symbols, as opposed to the 36 numeral/alphabetical symbols of the International Code plus a few Morse punctuations. They then had to learn to cope with the great speed of Japanese operators of up to 40-50 words per minute. To overcome the speed problem a form of shorthand was devised to record kana symbols, which also had to be learned. They also had to learn and write down in anglicised form, the phonetic Japanese sounds which matched each of the 71 kana symbols.

In all it was an extremely formidable task coupled with the essential need to copy accurately, the first time, the enemy's message. A repeat cannot be requested and an error in a crypto message can render code breaking difficult, or impossible. Hanging over this task was the concern that signals missed or unable to be decrypted or translated could lead to loss of lives. It was a matter of great pride that our RAAF kana operators became very good operators.

That initial group of 7 RAAF and 2 Army operators became proficient in their kana task after eight weeks of most concentrated and intensive training. Training completed, the RAAF operators set out for the eleven day trip to Darwin in early September 1941. They travelled by train to Adelaide, by the 'Ghan' to Alice Springs and by army truck to Darwin. On arrival they began work with two receiving sets at RAAF Darwin. To get their intercepted material back to Melbourne they had to encrypt it themselves and pass it to the RAAF general service communicators for onward transmission.

The RAAF interceptors at Darwin were reduced to four by illness when the early morning intercept shift on 19 February 1942 noted the abnormal traffic increases to and from Japanese bases north of Australia and from aircraft to carriers which Legion of Merit for exceptional meritorious service] and four of MacArthur's American interceptors evacuated from Corregidor. A few of the intercepts taken were handled on the spot but most were encrypted and rushed to the Central Bureau in Melbourne for processing and action.

No.1 Wireless Unit began its official life just two weeks before the battle of the Coral Sea. On 7th May 1942 the Japanese invasion force which intended to attack Port Moresby was intercepted by the Allied naval force and after a two day engagement the Japanese force returned to Rabaul. Port Moresby and as it turned out, Australia, had been spared. Coast watchers, aerial reconnaissance and Sigint had forewarned the Allies.

The next major Japanese naval battle was to be Midway where Yamamato intended to draw the American fleet into the Pacific and destroy it with his sheer weight of tonnage and aircraft. The outcome of the Midway battle was primarily determined by Sigint provided by the US navy intercept stations at Honolulu and Washington.

If, as is claimed, the Coral Sea Battle saved Australia, there is no doubt that the Battle of Midway, from the 4th to the 6th of June 1942 saved the United States in the Pacific. If the Japanese had won Midway the way would have been open for their carriers and battleships to isolate Hawaii, to rampage around the west coast of America and to threaten the Panama Canal. Whether the US would have been able to reinforce the SWPA at all would have been doubtful; at best it would have been delayed indefinitely. The consequence to Australia of that scenario would have been catastrophic. The usefulness of cryptanalysis and traffic analysis during the course of a sea battle, were proved beyond doubt at Midway.

In mid June the next 11 RAAF kana operators had graduated and arrived at Townsville to augment the embattled six at No. 1 Wireless Unit. Their training had been done in secretly set up classrooms under one of the outer ground stands flanking the arena at Melbourne Showgrounds. On 6th July the 13 members of the first WRAAF kana class completed their training at the Showgrounds and were posted to Point Cook where they intercepted point-to-point Japanese army and navy signal traffic from areas to the north and north-west of Australia.

By the 6th July the numbers of RAAF, WRAAF and American intercept operators available to MacArthur's Central Bureau had dramatically increased from the original        six to 29. They were in time for the desperate days ahead for the Allies in New Guinea and the Solomons; Port Moresby and Darwin.

MacArthur moved his HQ to Brisbane on 20th July 1942 and Central Bureau immediately followed.

The Allies' ability to penetrate the Japanese crypto systems was not always effective, due mainly to regular changes in keys. The severe American-Australian defeat in the naval battle of Savo Island is the best example because HMAS CANBERRA and three USN heavy cruisers were lost. Traffic analysis warned of the presence of the dangerous Japanese naval strike force assembling in the Solomons area but because of the difficulty following the crypto-key change to the Japanese naval code [JN25], the most vital signal, duly intercepted, was not able to be fully decrypted until after the event.

As the war in the SWPA rolled on the Sigint effort increased, more trained kana operators moved into the intercept field. Two new Wireless Units were set up for Darwin, one to handle naval-air and naval base-to-base and the second to cover army-air; and a detachment of No. 1 Wireless Unit went to Port Moresby.

By mid February 1943 the Japanese plans to reinforce the Lae area were an open book to the Sigint organisation. The Allies success at the battle of the Bismarck Sea was the result of being in prior possession of the enemy's intentions.

The loss of Admiral Yamamoto on 18th April 1943 was a turning point in Japan's war in the Pacific.

Late in June 1943 MacArthur's operation `Cartwheel' began, involving 13 separate amphibious landings along the northern coast of New Guinea and up the Solomons to Bougainville.

On 17th August 1943 General Kenney threw all his available USAF and RAAF aircraft at the 225 Japanese army bombers and fighters which were massed at their four Wewak airstrips to attack the Allies' northern New Guinea air bases. Through the 17th and 18th the Allies destroyed 150 Japanese aircraft, practically all their flight crews, thousands of drums of avgas and over 300 aircraft mechanics. Although the Japanese strove to replace their losses from the Philippines they ran out of aviation fuel and again the news of that shortage came through Sigint.

Four more RAAF Wireless Units were formed over the remaining two years of the Pacific War.

As the Japanese lost bases the Sigint and DF crews followed their retreat. Although MacArthur has been criticises as pro-American and not giving Australians credit for their part in his successes, he was extremely proud of his Australian-based Sigint organisation and the work his Australian troops did in New Guinea.

After the Australians captured Sio, which lies between Lae and Madang, troops using mine detectors to clear an area, uncovered several steel boxes in a deep, water-filled pit. When opened, they contained the current Japanese army high-grade code books, abandoned by the retreating Japanese commander. The Japanese were unaware of the / loss. For more than two months — February to March and into April 1944 — the find enable Central Bureau to decipher traffic in this top-level code, which had previously been very difficult, sometimes impossible to read, immediately on receipt, with devastating consequences for the enemy. Following on this fortunate occurrence, the Japanese army main line code problem was handled with almost continuous success until the surrender.

As General Kenney's 5th Air Force HQ began to follow the retreating Japanese, Kenney took his Australian No.1 Wireless Unit with him to provide the army and navy air intelligence cover.

Then came the drive to Japan via the Pacific Islands, which is omitted from this precis but which can be imagined. The Wireless Unit personnel ended up in the Philippines. The Eavesdroppers contains a very interesting section on Kamikaze operations out of the Philippines.

When the Kamikaze scheme was fully operational it became the greatest single problem for the Americans until the end of the war.

At 0845 on the morning of 6th August 1945 there was a sudden stop to traffic on important Japanese frequencies. When the interceptors heard that the atomic bomb had been dropped on Hiroshima they knew that they had, in fact, eavesdropped on a significant moment in history. When traffic started to flow again, early intercepts indicated that the Japanese had misread American intentions and believed that the bomb heralded the imminent invasion of Japan.

After the second bomb was dropped on Nagasaki on 9th August, Wireless Unit personnel recall that among the first messages from enemy HQ were directives to their outlying bases to immediately place all prisoners of war on at least normal Japanese soldier's rations and release all Red Cross parcels to them.

The Epilogue to The Eavesdroppers records that the closest Australian flag to Tokyo at war's end was being flown by the RAAF Wireless Unit members at San Miguel. They returned to Australia with the Australian Central Bureau personnel in a specially allocated American Liberty Ship Francis N. Blanchett, leaving Pier 15, Manila Bay waterfront, on 9th October 1945.

Before being discharged, all Wireless Unit and Central Bureau personnel were warned that their wartime activities must remain secret and were required to sign declarations to that effect. It is remarkable that, until Jack Bleakley retired and began researching his book in about 1985, the silence was maintained.