World War II

China, Burma, India: The CBI Theater

One of the authors of this report, Donald A. Borrmann, who served as a T/A Officer in India and China during WWII, furnished this information concerning the CBI.

The CBI Theater was important to the Allies in WWII but did not involve the numbers of U. S. troops that fought in Europe and the Pacific.

Lt. Donald A. Borrmann in India, 1945.

The U. S. strategic objectives were to maintain the Chinese Nationalist government’s ability to engage significant Japanese forces in China, to protect India from invasion, and to re-take Burma from the Japanese.

The CBI Theater Headquarters at New Delhi, India, included a unit of the Signals Intelligence Service (SIS) headed by Col. Leonard Bickwit. I know that the Allied effort to re-take Burma was given support from signals intelligence, including T/A, but I cannot furnish specifics because my own assignment involved Japanese forces in China, and the need-to-know security policy was very much in force during the war. Additionally, due to the nature of the fighting in Burma, with Allied irregular forces implanted in Japanese occupied areas, valuable intelligence also was provided by human sources (HUMINT).

Concerning Japanese forces in China, I can document a specific example of the value of T/A as follows: By early 1945 the Japanese army’s ‘Ichi Go’ offensive in China had succeeded in occupying the most forward bases (including Liuchow and Kweilin) of the U.S. Army 14th Air Force, which included some of the former members of the famous Flying Tigers unit. At that time the U.S. Army G-2 in New Delhi informed Col. Bickwit that he was receiving valuable signals intelligence on these Japanese forces in China and wished to know more about how it was produced. The source was T/A, so Col. Bickwit took me to brief the G-2 on how, through T/A on Japanese army communications, it was possible to continue to identify the Japanese army units involved and their changing locations. The elements addressed in the briefing included: analyzing the radio callsigns and address systems, the communications relationships, radio network structure and message flows, and also included radio direction finding. Despite this evidence of intelligence value, circumstances were such that there was no resultant change on the battlefield in this area of China. The intelligence was provided to U.S. Army 14th Air Force and to U.S. Army advisory group personnel attached to the Chinese Nationalist army, which contributed mostly defensive resistance to the Japanese. The Japanese were not defeated in China, but their forces there did surrender at war’s end.

The Pacific Theater

During WWII, COMINT, including T/A, played a vital role in the Pacific Ocean naval battles occurring as U. S. forces were “island hopping” westward to secure bases necessary to support later attacks on the Japanese home islands and to prevent further expansion of Japanese forces closer to Hawaii and Australia. Successful cryptanalysis of Japanese naval cipher messages was often temporarily unavailable due to Japanese cipher changes. Throughout these periods, T/A was relied on to maintain continuity on the identity of the Japanese military and naval units and their location and movements through message externals and RDF.

The China/Burma/India theater, WWII

In 1942 there was a great disparity in favor of Japan in the number of battleships, aircraft carriers, and cruisers available to each opposing force. During the spring of 1942, prior to the naval battle in the Coral Sea, the presence and movement of Japanese naval forces into the Solomon Islands area was revealed through T/A, including RDF.(14) Less than a month later in June 1942, prior to the battle of Midway Island, T/A contributed to identifying the presence of a Japanese air group in the Marshall Islands, and more importantly, T/A confirmed that the entire Japanese combined fleet was en route to Midway.(15) The Japanese attack on Midway Island on June 4, 1942, resulted in a vital U.S. victory.

The Central Pacific and Midway Island.

From August through December 1942, the Solomon Islands campaign included many engagements and actions between naval surface and submarine units and land and carrier-based aircraft. These included the U.S. landings on Tulagi and Guadalcanal islands and continuing Japanese efforts to land troop reinforcements by sea (the “Tokyo Express”) on Guadalcanal (through the channel known as “the Slot”). T/A made critical contributions during this period. Prior to the U.S. landings, T/A noted a marked increase in Japanese activity in the Solomons and provided identities of the Japanese naval units involved and not involved, all of which were of great value to U.S. preparations and reactions. After the U.S. landings in August 1942, T/A was able to give many advance warnings of the numerous nighttime “Tokyo Express” runs. Based on this information, the U.S. launched strikes, causing significant losses of Japanese ships, aircraft and troops, and forcing the eventual Japanese decision to withdraw their forces from Guadalcanal in February 1943. A quote from this period states: “The problem of attaining surprise and at the same time keeping track of enemy movements was immensely complicated by the fact that the Japanese on August 1 made a drastic change in their naval operation code, JN25, evidently scrambling the code groups.” That evening the keeper of the CinCPac Command Summary wrote: “We must depend almost entirely on traffic analysis to deduce the enemy deployment.”(16)

The Southwest Pacific Theater

General MacArthur became commander of the Southwest Pacific Theater after his arrival in Australia from Corregidor. SIGINT capabilities were provided in this area by Central Bureau Brisbane (CBB, a joint U.S. and Australian organization) and by the U.S. Navy’s Fleet Radio Unit Melbourne (FRUMEL). These organizations provided important support as MacArthur’s forces moved against the Japanese in New Guinea, bypassing and isolating Japanese units in many locations, and eventually retaking the Philippine Islands in conjunction with the U.S. Navy (also see Illustration 6).

A description of intelligence support provided by these units to MacArthur appears in an NSA history document, which states: “Traffic analysis activities were the first step in compiling an accurate Japanese order of battle. There were many instances during the war when traffic analysis was MacArthur’s only source of signals intelligence because codes were unreadable at the time. One instance was the Japanese attack on Port Moresby, New Guinea, in July 1942. Another time traffic analysis had to fill the void was when the Japanese army changed their codes on 8 April 1944, as MacArthur was planning the Hollandia invasion, which was to begin on April 22, 1944.”(17)

Generally T/A was able to provide accurate prediction of attacks, identify Japanese units involved, and describe Japanese troop deployments. One such instance included increased activity at Wewak in August 1943 and movement of a Japanese headquarters from Rabaul to Wewak, enabling the U.S. Army Air Force to destroy some 200 Japanese aircraft within two days. T/A forecast the Japanese intention to reinforce the island of Morotai in 1944 and the intended move of a major Japanese army headquarters from Manila to Saigon in November 1944 (later confirmed by a decrypted message).

The Solomon Islands, Coral Sea,
and Southwest Pacific. Frederick Parker, A Priceless Advantage:
U.S. Navy Communications Intelligence and the Battles

The Battle of the North Atlantic

The German U-boat campaign against Allied shipping in the North Atlantic early in WWII was very successful in its initial stages. An average of about 500,000 shipping tons per month were lost to the U-boats between January and September 1942, and there was a serious and real concern that Great Britain would not survive if this trend continued.(18) The Allies initiated a variety of actions to stem the losses inflicted by the U-boats and to ensure that a steady flow of critical supplies safely reached the British Isles.

Large circularly disposed antenna array used
for radio direction finding and intercept.

These actions resulted in a complete turn-around of fortunes in the North Atlantic, and German Admiral Donitz, commander of the U-boat fleet, was forced to change the focus of his efforts away from that area. Radio Direction Finding was one of the principal tools employed in this successfully coordinated approach, along with decryption of messages (ULTRA), radar, sonar, T/A and the increased range of land-based aircraft. Every one of these efforts contributed significantly, but, in combination, it made individual efforts extremely difficult to distinguish. This complex atmosphere had the salutary effect of “covering” the singular contributions of individual efforts and especially of the super-sensitive ULTRA source. It also prevented Admiral Donitz from determining exactly what was contributing to the high German losses.

Two distinct aspects of RDF were used in the North Atlantic. One was land based and the other mobile. Land-based H/F D/F operations, sometimes referred to as “Huff Duff,” often employed large antennas. (Illustration 9 shows a more recent version of an antenna called a circularly disposed antenna array or CDAA which was used for radio intercept as well as D/F. These were so large they were referred to as “elephant cages.” By contrast, illustration 2 shows a WWI land-based mobile D/F operation). D/F information from land-based sites was more strategic and was used to re-route convoys to avoid U-boat activity. Land-based D/F also was used to locate German resupply operations where supply submarines, referred to as “milch cows,” were replenishing fuel and other supplies on board the attack submarines.

German Enigma message referring to D/F.

Most of the mobile RDF in the North Atlantic was shipborne D/F and was used extensively in tactical operations. On occasion a location or “fix” could be obtained by using cross bearings from multiple sources and then convoy escorts or even aircraft in the area could be vectored to the target. There are other occasions where an escort ship would get a line bearing from its own D/F unit and follow the line until it spotted the submarine, then initiated an attack. Line bearings from mobile naval D/F units normally were a maximum of thirty miles in length; therefore, the surface ship would expect to find the target along the prescribed line and within thirty miles. Again, although it is difficult to tally exactly the results of D/F because of the variety of information also available from other sources, it is safe to say that D/F made significant contributions to the successful prosecution of the Battle of the North Atlantic. Illustration 10 shows the German awareness of their vulnerability to D/F.

Notes 14-18

14. E. B. Porter, Nimitz (Annapolis, MD: Naval Institute Press, 1976), 69, 88, and Roland Lewin, The American Magic (Penguin Books, 1984), 93.

15. Lewin, 144, 155, 165, 166.

16. Porter, 179.

17. Sharon Maneki, The Quiet Heroes of the Southwest Pacific Theater: An Oral History of the Men and Women of CBB and FRUMEL, NSA Center for Cryptologic History (1996), Preface.
18. Kathleen Broome Williams, Secret Weapon: U.S. High-Frequency Direction Finding in the Battle of the Atlantic (Annapolis, MD: Naval Institute Press, 1996), 23.

Source: Center for Cryptologic History National Security Agency