United States Army in World War II: Special Studies

Manhattan: The Army and the Atomic Bomb

By Vincent C. Jones


. . . to Those Who Served

Table of Contents



Prologue: A History of Atomic Energy to 1939

Uranium and Fission – Efforts To Enlist Support of the U.S. Government

Part One: Beginnings of the Atomic Mission

Chapter 1: The Army and the Atomic Energy Program, 1939–1942

Origins of the Army’s Role – Decision To Develop Atomic Weapons – Establishment of the NDRC and OSRD – New Advances in Atomic Research, 1940–1941 – Top Policy Group: Preparing for Army Take Over – Progress in Research and Development: The Nuclear Steeplechase

Chapter 2: Establishing the Manhattan District

Organizing the District – Army-OSRD Planning Meeting, 25 June 1942 – Progress in Research and Development

Chapter 3: First Steps for Weapon Development

Securing an Architect-Engineer-Manager – Obtaining Funds – Securing a Priority Rating – Procuring Essential Materials – Site Selection – Reaching Decisions: The Meeting at Bohemian Grove

Chapter 4: General Groves Takes Command

Reorganization and the Selection of Groves – First Measures – Establishment of Los Alamos – Manhattan Project Organization and Operation

Part Two: Producing Fissionable Materials

Chapter 5: Organizing for Production

Plutonium Project – Reassessment of Processes To Produce a Bomb – Contract Negotiations – Hanford Engineer Works – Plutonium Semiworks: Argonne vs. Tennessee – Program Funding

Chapter 6: The Electromagnetic Process

Electromagnetic Research and the Army, 1942–1943 – Research and Development, 1943–1945: Radiation Laboratory – Design and Engineering, 1943–1945 – Building the Electromagnetic Plant – Plant Operation

Chapter 7: The Gaseous Diffusion Process

Gaseous Diffusion Research and the Army, 1942–1943 – Design and Engineering – Building the Gaseous Diffusion Plant – Plant Operation

Chapter 8: The Liquid Thermal Diffusion Process

Research and Development: The Role of the Navy – Reassessment: Decision for Full-scale Development – Plant Design, Engineering, and Construction – Plant Operation

Chapter 9: The Pile Process

Research and Development: Metallurgical Laboratory – Organization for Plutonium Production – The Semiworks: Clinton Laboratories – The Hanford Production Plant

Part Three: Support Activities

Chapter 10: Anglo-American Collaboration

Breakdown of Interchange – The Quebec Agreement – Implementing the Agreement – New Partnership Strains: Repatriation of French Scientists

Chapter 11: Security

Early Aspects – The District’s Security System – Counterintelligence Activities – Safeguarding Military Information

Chapter 12: Foreign Intelligence Operations

Organization of the Alsos Mission – Alsos Operations in Italy – Manhattan’s Special Intelligence Activities, 1944 – Alsos Operations in Western Europe, 1944–1945

Chapter 13: The Raw Materials Program

Geographic Search and Field Exploration – Ore Control Agency: Combined Development Trust – Ore Acquisition in Foreign Areas

Chapter 14: The Feed Materials Program

Program Organization and Support Activities – Feed Materials Procurement – Feed Materials Production – Quality Control Program

Chapter 15: Land Acquisition

Clinton Engineer Works – Los Alamos – Hanford Engineer Works – Other Sites

Chapter 16: Manpower Procurement

Personnel Organization – Scientific and Technical Personnel – Industrial Labor – Civilian and Military Personnel

Chapter 17: Manpower Conservation

Labor Turnover: The Problem and Its Cure – Special Problems With the Selective Service System – Labor Relations: Union Activities and Work Stoppages

Chapter 18: Electric Power

Power Requirements and Sources – Implementation of the Power Program – Distribution: Clinton Engineer Works – Distribution: Hanford Engineer Works

Chapter 19: Communications and Transportation

Communications – Transportation

Chapter 20: Health and Safety

The Health Program – The Safety Program

Chapter 21: The Atomic Communities in Tennessee

Oak Ridge: The Operating Community – The Construction Camps – Community Management

Chapter 22: The Atomic Communities in Washington State

Selecting Sites – Hanford: The Construction Camp – Richland: The Operating Community – Community Management

Chapter 23: The Atomic Communities in New Mexico

Los Alamos: The Operating Community – Trinity: The Base Camp

Part Four: The Bomb

Chapter 24: The Los Alamos Weapon Program

Planning Phase – Laboratory Administration – Post Administration

Chapter 25: Weapon Development and Testing

Building the Bomb – Project Trinity: The Test of the Bomb

Chapter 26: The Atomic Bombing of Japan

Preparations for an Atomic Bombing Mission – The Decision To Use the Bomb – Dropping the Bomb – The Surrender of Japan – Survey of the Bombing Effects

Part Five: Completing the Atomic Mission

Chapter 27: The Atomic Age and its Problems

The Atomic Story: Informing the Public – Atomic Energy: Planning for Postwar Control

Chapter 28: The Army and the Atomic Energy Program

1945–1947 – A Postwar Trusteeship – The Final Act: Transfer to Civilian Control

Epilogue: An Atomic Legacy

Appendix – Einstein’s Letter

Bibliographical Note

Guide to Archival Collections

List of Abbreviations



1. Stone and Webster Engineering and Design Personnel

2. Land Acquisition at CEW, 1942–1944

3. Comparative Estimates of Atomic Bombing Casualties in World War II


1. Organization of the Manhattan Project, April 1943

2. Organization of the Manhattan District, August 1943

3. Organization of the Manhattan District, January 1945

4. Feed Materials Network, January 1945

5. Estimated Officer Personnel Requirements for the

Manhattan District, January 1943


1. Projected Site for Atomic Production Plants, Tennessee, 1942

2. Manhattan Project, 1942–1946

3. Clinton Engineer Works, Tennessee, 1943–1945

4. Hanford Engineer Works, Washington, 1943–1945

5. Los Alamos Site, New Mexico, 1943–1945

6. Trinity Test Site, 1945

7. The Atomic Bombing of Japan, August 1945


Maj. Gen. Leslie R. Groves – Ernest O. Lawrence, Arthur H. Compton, Vannevar Bush, – and James B. Conant – Secretary of War Henry L. Stimson – Brig. Gen. Wilhelm D. Styer – Brig. Gen. James C. Marshall – Col. Kenneth D. Nichols – Silver-wound Magnet Coils for the Electromagnetic Process – Approach Road to the Los Alamos Ranch School for Boys – Manhattan Project Emblem – Mrs. Jean O’Leary and General Groves – Col. E. H. Marsden – Excavation at the Tennessee Site – Alpha I Racetrack, Electromagnetic Plant, CEW – Electromagnetic Plant Under Construction – CEW Training Facilities – Electromagnetic Plant in Full Operation – Gaseous Diffusion Plant Under Construction, CEW – K-25 Steel-frame Construction – Completed Plant Section – Completed Gaseous Diffusion Plant – Richard C. Tolman – Liquid Thermal Diffusion Plant, CEW – Billboard at the S-50 Plant Site – University of Chicago Physics Building – Argonne Laboratory Near Chicago – 124th Field Artillery Armory in Chicago – New Chemistry Building, Metallurgical Laboratory, Chicago – Heavy Water Plant at the Wabash River Ordnance Works – Maj. Arthur V. Peterson – Clinton Laboratories Pilot Pile, CEW – Clinton Laboratories – 300 Area, HEW – 100 B Pile Area, HEW – Chemical Separation Plant Under Construction, HEW – Completed Chemical Separation Plants – Sir James Chadwick, General Groves, and Richard Tolman – Changing of the Guard, CEW – Security Sign at the Tennessee Site – Farm at the Tennessee Site – Typical Terrain of the Los Alamos Site – Military and Civilian Workers, CEW – Women’s Army Corps Detachment, CEW – Enlisted Men at CEW During Off-Duty Hours – Large Troop Contingent at Los Alamos on Parade – Power Plant, HEW – K-25 Power Plant, CEW – Unimproved Santa Fe-Los Alamos Road – Improved Santa Fe-Los Alamos Road – Oak Ridge Bus Terminal – Gallaher Bridge Road at the Tennessee Site – Col. Stafford L. Warren – Hazardous Materials Storage Area, Los Alamos – Oak Ridge Hospital – Oak Ridge Shopping Mall and District Headquarters – Black Workers, CEW – Prefabricated Houses and Apartment Dwellings, CEW – Enlisted Men’s Barracks, CEW – Gamble Valley Trailer Camp, CEW – Oak Ridge Elementary School 444 – Main Post Office and Theater in Oak Ridge – CEW Reservation Entry Point – Chapel-on-the-Hill in Oak Ridge – Hanford Construction Camp, HEW – Camp Administrative and Residential Areas, HEW – Richland Village, HEW – Typical Building at the Los Alamos Ranch School – Family Apartment Units at Los Alamos – Military Mess Facility at Los Alamos – Los Alamos Ranch Trading Post – Street Scene in Los Alamos – Pupils at the Los Alamos Community School – Trinity Base Camp – J. Robert Oppenheimer – Lt. Col. Curtis A. Nelson – Technical Area at Los Alamos – Brig. Gen. Thomas A. Farrell and General Groves – Trinity Control Dugout and Observation Post – The Atomic Explosion at Trinity, 16 July 1945 – Little Boy – Fat Man – Col. Elmer E. Kirkpatrick, Jr. – General Groves Checking Location of Bombing Targets – Col. Paul W. Tibbets, Jr., and Ground Crew at Tinian – Enola Gay at Tinian – Mushroom Cloud Over Hiroshima – Physical Damage at Hiroshima – Atomic Bombing Casualties at Nagasaki – Survivors of the Nagasaki Bombing – General Groves Holding a Press Conference – Henry D. Smyth and Richard Tolman – Oppenheimer Congratulating the Troops – Secretary of War Robert P. Patterson and General Groves – Transfer of Control to the Atomic Energy Commission.

Illustrations courtesy of the following sources: p. 89 from Typography and Design Division, Government Printing Office; pp. 361, 474, and 582 from Col. Gerald T. Tyler; and p. 600 from Wide World Photos. All other illustrations are from the files of the Department of Defense and the Department of Energy.

U.S. Army Center of Military History

Brig. Gen. Douglas Kinnard, USA (Ret.), Chief of Military History

David F. Trask, Chief Historian

Col. James W. Dunn, Chief, Histories Division

John W. Elsberg, Editor in Chief