Preface - V [Marine] Amphibious Corps Planning for Operation Olympic and the Role of Intelligence in Support of Planning.

EXECUTIVE SUMMARY
Title: V [Marine] Amphibious Corps Planning for Operation Olympic and the Role of Intelligence in Support of Planning.
Author: Major Mark P. Arens, USMCR [MCIA]
Thesis: That the intelligence estimates of the Japanese forces and their capabilities on Kyushu, for Operation Olympic, were so inaccurate that an amphibious assault by the V Amphibious Corps would have failed.
Discussion: This research paper, while addressing events at the strategic and operational level, will concentrate primarily on the V Amphibious Corps, one of four corps comprising the ground assault force in Operation Olympic, the projected invasion of Kyushu, Japan, in November 1945. It will focus on the planning phase of the operation and the intelligence used in that process.
Chapter One introduces the U.S. Pacific strategy in 1945 and highlights the reasons for the decision to invade the Japanese home islands. Based on the policy of unconditional surrender, U.S. policymakers implemented Operation Downfall, a series of operations to decisively defeat Imperial Japan. The first operation planned was Operation Olympic, the invasion of Kyushu by the U.S. Sixth Army. The Sixth Army was to be comprised of four corps, one being the V Amphibious Corps.
Chapter Two discusses the role of the V Amphibious Corps in Operation Olympic. Composed of the Second, Third and Fifth Marine Divisions, V Amphibious Corps was to conduct an assault on the southwestern coast of Kyushu. Kyushu is a mountainous island with difficult terrain that restricts maneuver. This chapter also addresses the planning process and the concept of operations of this Corps. Finally, it covers the training regimen that was preparing the Marines of V Amphibious Corps for the final fight.
Chapter Three details the intelligence that U.S. planners had in which to develop their operational plans. It tracks the development of the intelligence picture from early 1945 to the end of the war in August 1945. It focuses on the intelligence that V Amphibious Corps had for planning. This chapter also highlights some of the differences in the analysis of the information. The chapter ends with a summary of the U.S. intelligence sources, methods, and organizations used to collect and analyze the intelligence information concerning Japanese defenses on Kyushu.
Chapter Four is derived from the Japanese defensive plans for Kyushu obtained during the U.S. occupation of Japan after the war. Code-named Ketsu-Go, the Japanese operation to defend Kyushu was to be the final decisive battle. The Japanese intended to break the will of the American people to continue the war by inflicting tremendous casualties on the invasion force. This chapter focuses on the defenses on Satsuma peninsula, the location of the V Amphibious Corps landing beaches.
Chapter Five is the conclusion where the role of intelligence in support of planning is analyzed, based upon the true Japanese defensive posture identified in chapter four. The V Amphibious Corps' concept of operations is also analyzed reflecting the terrain restrictions and the Japanese defensive strategy. Finally, the paper ends with a discussion on the estimated casualty rates if Operation Olympic would have been executed.

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THE OPINIONS AND CONCLUSIONS EXPRESSED HEREIN ARE THOSE OF THE INDIVIDUAL STUDENT AUTHOR AND DO NOT NECESSARILY REPRESENT THE VIEWS OF EITHER THE MARINE CORPS COMMAND AND STAFF COLLEGE OR ANY OTHER GOVERNMENTAL AGENCY.

PREFACE
In 1995, the world celebrated the 50th anniversary of the end of World War II. Popular print media as well as scholarly journals presented timely articles on a wide range of topics concerning the war. Probably the most controversial subject though, concerned President Truman's decision to drop atomic bombs on Japan. The authors of these articles would usually take a side, either supporting or criticizing Truman's decision. Common to all of the articles though, was a reference to the planned invasion of the Japanese home islands, Operation Olympic, and the casualties associated with that invasion. In discussing the casualties, the authors presented numerous and disparate casualty figures, based on many different sources. While the casualty figures were usually derived from valid sources, little effort was made to analyze how the military and government officials arrived at those numbers. The majority of the articles did not address the specifics of Olympic, or the Japanese defenses.
This paper closely examines the operational planning for Operation Olympic and the intelligence information which supported that planning. While it addresses the U.S. strategy in the Pacific in 1945, it primarily focuses on the planning for the invasion of the island of Kyushu. Starting at the macro level of looking at the entire operation, it transitions to the micro level of analyzing the planning of the Marines of the V Amphibious Corps. This study also looks at the intelligence information that U.S. planners had in the summer of 1945, and compares that with the actual Japanese defense plans and disposition of forces on Kyushu. Through this analysis and comparison, a conclusion is drawn that if Operation Olympic had been executed, as planned, on
1 November 1945, a devastating bloodbath would have occurred for both the U.S. and Japanese forces.
The operational plans, staff studies and intelligence estimates produced by General MacArthur's staff, Admiral Nimitz's staff, the U.S. Sixth Army, V Amphibious Corps, and various Navy commands in the Pacific were used as primary sources. Also used as a primary source were records from the U.S. forces that occupied Japan at the end of the war. These reports were invaluable in compiling the Japanese defense plan and force disposition on Kyushu. These sources are located at the National Archives and Naval Historical Center in Washington, DC, and at the Marine Corps Research Center in Quantico, VA. Many books on World War II and recently published articles concerning the end of the war with Japan were utilized as secondary sources.
Finally, I wish to express my sincere thanks to my mentors, Dr. Donald F. Bitner, Professor of Military History, U.S. Marine Corps Command & Staff College, and Ms. A. Kerry Strong, Archivist, Marine Corps Research Center, for their patience and guidance. Their advice was of great benefit to my research and writing effort