MacArthur's ULTRA: Codebreaking and the War against Japan, 1942-1945 / Edition 1

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Cracking the enemy's radio code is a task so urgent and so difficult that it demands the military's best minds and most sophisticated technology. But when the coded messages are in a language as complex as Japanese, decoding problems multiply dramatically.

It took the U.S. Army a full two years after the attack on Pearl Harbor to break the codes of the Japanese Imperial Army. But by 1944 the U.S. was decoding more than 20,000 messages a month filled with information about enemy movements, strategy, fortifications, troop strengths, and supply convoys.

In MacArthur's ULTRA, historian Edward Drea recounts the story behind the Army's painstaking decryption operation and its dramatic breakthrough. He demonstrates how ULTRA (intelligence from decrypted Japanese radio communications) shaped MacArthur's operations in New Guinea and the Philippines and its effect on the outcome of World War II.

From sources on both sides of the Pacific and national security agency declassified records, Drea has compiled a detailed listing of the ULTRA intelligence available to MacArthur. By correlating the existing intelligence with MacArthur's operational decisions, Drea shows how MacArthur usedand misusedintelligence information. He tells for the first time the story behind MacArthur's bold leap to Hollandia in 1944 and shows how ULTRA revealed the massive Japanese mobilization for what might have been (had it occurred) the bloodiest and most protracted engagement of the entire war the Allied invasion of Japan. Drea also clarifies the role of ULTRA in Truman's decision to drop atomic bombs on Japan in 1945, and concludes that ULTRA shortened the war by six to ten months.

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Editorial Reviews

A must for anyone with more than a superficial interest in World War II or military history. This is the first comprehensive examination of General Douglas MacArthur's use of ULTRA. Drea's use of primary sources and secondary Japanese material results in a balanced picture that gives both sides of the story. Particularly fascinating is his description of the Japanese codes themselves and how they were decoded by MacArthur's Central Bureau.
A superb book that will surely be the prime reference work on the subject for years to come.
Publishers Weekly - Publisher's Weekly
The acronym ``ULTRA,'' as employed here, refers to special intelligence derived from the interception and decryption of Japanese radio traffic and its use by Gen. Douglas MacArthur in his New Guinea and Philippines campaigns. Drea's excellent study uncovers the motivation behind certain command decisions that have puzzled historians, particularly in regard to the 1944 Hollandia operation in New Guinea. He demonstrates how ULTRA enabled MacArthur to select the weakest point in the enemy's defenses and then strike with overwhelming superiority. On the other hand, Drea also shows that MacArthur's use of ULTRA became a ``hit or miss proposition'' after Hollandia, and comes to the surprising conclusion that the general did not rely heavily on ULTRA, usually dismissing intelligence that failed to mesh with his preconceived strategic vision. The book presents a detailed illustration of the interplay between intelligence-gathering and operational planning, and uses one of history's most successful commanders as its model. Drea is chief of the research and analysis division at the Army Center of Military History in Washington, D.C. Photos. (Dec.)
Library Journal
Ten years after the appearance of Ronald Lewin's The American Magic: Codes, Ciphers, and the Defeat of Japan ( LJ 1/1/82), Drea has produced a revisionist view of American strategy and decision-making in the Pacific theater of World War II. Drea posits that MacArthur's access to ULTRA radio intercepts and decoding gave him an enormous advantage over the Japanese, an advantage he did not always employ. The ``American Caesar'' tended to believe radio intercepts that reinforced his preconceptions of Japanese resources and strategy at the expense of other intelligence. The decision to employ atomic weapons against Japan is presented as based upon analysis of Japanese anti-invasion defenses, and MacArthur's postwar flip-flop--his criticism of the use of atomic weapons--is seen as consistent with his pattern of intelligence use and misuse. This important study belongs in all World War II collections, but readers unfamiliar with events in the Pacific theater might be advised to keep one of the single-volume histories of the war at hand, since Drea is more interested in documenting decision-making than in producing a traditional campaign history. Previewed in ``The Day of Infamy in Print,'' LJ 9/1/91, p. 206-7.-- Stanley Planton, Ohio Univ.-Chillicothe Lib.
A lucid account of the process of machine translation. Nagao (engineering, Kyoto U) details recent developments in MT systems and makes suggestions for their utilization. The book will interest general readers. Surveys current intellectual activity in machine translation. It is the first book to provide detailed accounts of five different methodologies for machine translation research developed in Europe and Japan as well as the United States and Canada. Of particular interest are chapters on the Japanese Government Machine Translation Project and on the European Economic Community's EUROTRA program. Paper ed. $17.95. Drea recounts the story behind the Army's painstaking decryption operation and its dramatic breakthrough. He demonstrates how ULTRA (intelligence from decrypted Japanese radio communications) shaped MacArthur's operations in New Guinea and the Philippines and its effect on the outcome of World War II. Annotation c. Book News, Inc., Portland, OR (
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Product Details

  • ISBN-13: 9780700605767
  • Publisher: University Press of Kansas
  • Publication date: 12/28/1991
  • Series: Modern War Studies Series
  • Edition description: New Edition
  • Edition number: 1
  • Pages: 312
  • Sales rank: 526,524
  • Product dimensions: 6.00 (w) x 9.01 (h) x 0.89 (d)

Table of Contents

List of Illustrations and Tables


1. MacArthur's Codebreaking Organization

2. ULTRA's Trials and Errors, 1942

3. Breaking into the Japanese Army Codes, January 1943 - January 1944

4. ULTRA's Great Victory: The Hollandia Operation, January - April 1944

5. Misreading ULTRA, May - September 1944

6. The Missing Division: Leyte, 1944

7. The Numbers Game: Luzon, January - June 1945

8. ULTRA as Seer: Uncovering Japanese Plans for Homeland Defense, June - August 1945

9. Conclusion


A Note on Sources

Selected Bibliography


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