Editing Manhattan Project (section)

== Organization ==

=== Manhattan District ===
The [[Chief of Engineers]], Major General [[Eugene Reybold]], selected Colonel [[James C. Marshall]] to head the Army's part of the project in June 1942. Marshall created a liaison office in Washington, D.C., but established his temporary headquarters at [[Tower 270|270 Broadway]] in New York, where he could draw on administrative support from the Corps of Engineers' [[North Atlantic Division]]. It was close to the Manhattan office of [[Stone & Webster]], the principal project contractor, and to Columbia University. He had permission to draw on his former command, the Syracuse District, for staff, and he started with [[Lieutenant Colonel (United States)|Lieutenant Colonel]] [[Kenneth Nichols]], who became his deputy.<ref name="NYT">{{cite news |last=Broad |first=William J. |url=https://www.nytimes.com/2007/10/30/science/30manh.html |title=Why They Called It the Manhattan Project |newspaper=[[The New York Times]] |date=30 October 2007 |access-date=27 October 2010}}</ref><ref name="Jones, pp. 41-44">{{harvnb|Jones|1985|pp=41–44}}.</ref>

[[File:Manhttan Project Organization Chart.gif|thumb|The Manhattan Project Organizational Chart, 1 May 1946|alt=Organization chart of the project, showing project headquarters divisions at the top, Manhattan District in the middle, and field offices at the bottom]]
Because most of his task involved construction, Marshall worked in cooperation with the head of the Corps of Engineers Construction Division, Major General [[Thomas M. Robins]], and his deputy, Colonel [[Leslie Groves]]. Reybold, Somervell, and Styer decided to call the project "Development of Substitute Materials", but Groves felt that this would draw attention. Since engineer districts normally carried the name of the city where they were located, Marshall and Groves agreed to name the Army's component the Manhattan District; Reybold officially created this district on 13 August. Informally, it was known as the Manhattan Engineer District, or MED. Unlike other districts, it had no geographic boundaries, and Marshall had the authority of a division engineer. Development of Substitute Materials remained as the official codename of the project as a whole but was supplanted over time by "Manhattan".<ref name="Jones, pp. 41-44" />{{sfn|Sullivan|2016|pp=86–87}}

Marshall later conceded that, "I had never heard of atomic fission but I did know that you could not build much of a plant, much less four of them for $90&nbsp;million."<ref>{{harvnb|Fine|Remington|1972|p=652}}.</ref> A single [[trinitrotoluene|TNT]] plant that Nichols had recently built in Pennsylvania had cost $128&nbsp;million.<ref>{{harvnb|Nichols|1987|p=174}}.</ref> Nor were they impressed with estimates to the nearest order of magnitude, which Groves compared with telling a caterer to prepare for between ten and a thousand guests.<ref>{{harvnb|Groves|1962|p=40}}.</ref> A [[surveying|survey team]] from Stone & Webster had already scouted a site for the production plants. The [[War Production Board]] recommended sites around [[Knoxville, Tennessee]], an isolated area where the [[Tennessee Valley Authority]] could supply ample electric power and the rivers could provide cooling water for the reactors. After examining several sites, the survey team selected one near [[Elza, Tennessee]]. Conant advised that it be acquired at once, Styer agreed, but Marshall temporized, awaiting the results of Conant's reactor experiments.<ref>{{harvnb|Hewlett|Anderson|1962|pp=76–78}}.</ref> Of the prospective processes, only Lawrence's electromagnetic separation appeared sufficiently advanced for construction to commence.<ref>{{harvnb|Fine|Remington|1972|p=654}}.</ref>

Marshall and Nichols began assembling the necessary resources. The first step was to obtain a high priority rating for the project. The top ratings were AA-1 through AA-4 in descending order, although there was a special AAA rating reserved for emergencies. Ratings AA-1 and AA-2 were for essential weapons and equipment, so Colonel [[Lucius D. Clay]], the deputy chief of staff at Services and Supply for requirements and resources, felt that the highest rating he could assign was AA-3, although he was willing to provide a AAA rating on request for critical materials if the need arose.<ref>{{harvnb|Jones|1985|pp=57–61}}.</ref> Nichols and Marshall were disappointed; AA-3 was the same priority as Nichols' TNT plant in Pennsylvania.<ref name="Fine 1972 657">{{harvnb|Fine|Remington|1972|p=657}}.</ref>

=== Military Policy Committee ===
[[File:Trinity Test - Oppenheimer and Groves at Ground Zero 002.jpg|thumb|upright|[[J. Robert Oppenheimer|Oppenheimer]] and Groves at the remains of the [[Trinity (nuclear test)|Trinity test]] in September 1945, two months after the test blast and just after the end of World War II. The white overshoes prevented fallout from sticking to the soles of their shoes.<ref>{{cite magazine |magazine=[[Time (magazine)|Time]] |date=17 September 1945 |url=https://content.time.com/time/subscriber/article/0,33009,854500,00.html |title=Science:Atomic Footprint |access-date=19 January 2022}}</ref>|alt=A man smiling in a suit in suit and one in a uniform chat around a pile of twisted metal.]]
Vannevar Bush became dissatisfied with Colonel Marshall's failure to get the project moving forward expeditiously<ref>{{harvnb|Hewlett|Anderson|1962|p=81}}.</ref> and felt that more aggressive leadership was required. He spoke to [[Harvey Bundy]] and Generals Marshall, Somervell, and Styer about his concerns, advocating that the project be placed under a senior policy committee, with a prestigious officer, preferably Styer, as director.<ref name="Fine 1972 657" />

Somervell and Styer selected Groves for the post; General Marshall ordered that he be promoted to brigadier general,<ref name="Jones, pp. 74-77">{{harvnb|Jones|1985|pp=74–77}}.</ref> as it was felt that the title "general" would hold more sway with the academic scientists working on the project.<ref name="Groves, pp. 4-5">{{harvnb|Groves|1962|pp=4–5}}.</ref> Groves' orders placed him directly under Somervell rather than Reybold, with Colonel Marshall now answerable to Groves.<ref>{{harvnb|Fine|Remington|1972|pp=659–661}}.</ref> Groves established his headquarters in Washington, D.C., in the [[Harry S. Truman Building|New War Department Building]], where Colonel Marshall had his liaison office.<ref>{{harvnb|Groves|1962|pp=27–28}}.</ref> He assumed command of the Manhattan Project on 23 September 1942. Later that day, he attended a meeting called by Stimson, which established a Military Policy Committee, responsible to the Top Policy Group, consisting of Bush (with Conant as an alternate), Styer and [[Rear Admiral (United States)|Rear Admiral]] [[William R. Purnell]].<ref name="Jones, pp. 74-77" /> Tolman and Conant were later appointed as Groves' scientific advisers.<ref>{{harvnb|Groves|1962|pp=44–45}}.</ref>

On 19 September, Groves went to [[Donald M. Nelson|Donald Nelson]], the chairman of the War Production Board, and asked for broad authority to issue a AAA rating whenever it was required. Nelson initially balked but quickly caved in when Groves threatened to go to the President.<ref>{{harvnb|Groves|1962|pp=22–23}}.</ref> Groves promised not to use the AAA rating unless it was necessary. It soon transpired that for the routine requirements of the project the AAA rating was too high but the AA-3 rating was too low. After a long campaign, Groves finally received AA-1 authority on 1 July 1944.<ref>{{harvnb|Jones|1985|pp=80–82}}.</ref> According to Groves, "In Washington you became aware of the importance of top priority. Most everything proposed in the Roosevelt administration would have top priority. That would last for about a week or two and then something else would get top priority".{{sfn|Ermenc|1989|p=238}}

One of Groves' early problems was to find a director for [[Project Y]], the group that would design and build the bomb. The obvious choice was one of the three laboratory heads, Urey, Lawrence, or Arthur Compton, but they could not be spared. Compton recommended Oppenheimer, who was already intimately familiar with the bomb design concepts. However, Oppenheimer had little administrative experience, and, unlike Urey, Lawrence, and Compton, had not won a Nobel Prize, which many scientists felt that the head of such an important laboratory should have. There were also concerns about Oppenheimer's security status, as many of his associates were [[Communism|communists]], including his wife, [[Katherine Oppenheimer|Kitty]]; his girlfriend, [[Jean Tatlock]]; and his brother, [[Frank Oppenheimer|Frank]]. A long conversation in October 1942 convinced Groves and Nichols that Oppenheimer thoroughly understood the issues involved in setting up a laboratory in a remote area and should be appointed as its director. Groves personally waived the security requirements and issued Oppenheimer's clearance on 20 July 1943.<ref>{{harvnb|Groves|1962|pp=61–63}}.</ref><ref>{{harvnb|Nichols|1987|pp=72–73}}.</ref>

=== Collaboration with the United Kingdom ===
{{Main|British contribution to the Manhattan Project}}
The British and Americans exchanged nuclear information but did not initially combine their efforts; in 1940–41 the British project ([[Tube Alloys]]) was larger and more advanced.{{sfn|Phelps|2010|pp=282–283}} British leadership initially opposed an offer by Bush and Conant in August 1941 to pool the nations' atomic efforts,{{sfn|Farmelo|2013|pp=188–195}} but the British, who had made significant advances in research early in the war, did not have the resources to carry it into development while devoting a large portion of their economy to the war; Tube Alloys soon fell behind its American counterpart.{{sfn|Bernstein|1976|pp=206–208}} The roles of the two countries were reversed,{{sfn|Villa|1981|pp=144–145}} and in January 1943 Conant notified the British that they would no longer receive atomic information except in certain areas.{{sfn|Stacey|1970|p=517}}{{sfn|Bernstein|1976|p=211}} The British investigated the possibility of an independent nuclear program but determined that it could not be ready in time to impact the [[European Theatre of World War II|war in Europe]].<ref name="fakley1983">{{cite journal |url=http://www.atomicarchive.com/History/british/index.shtml |title=The British Mission |author=Fakley, Dennis C. |journal=Los Alamos Science |date=Winter–Spring 1983 |issue=7 |pages=186–189}}</ref>

[[File:Groves and Chadwick 830308.jpg|thumb|left|Groves confers with [[James Chadwick]], the head of the British Mission.|alt=A large man in uniform and a bespectacled thin man in a suit and tie sit at a desk.]]
By March 1943 Conant decided that [[James Chadwick]] and one or two other British scientists were important enough that the bomb design team at Los Alamos needed them, despite the risk of revealing weapon design secrets.{{sfn|Bernstein|1976|pp=213}} In August 1943 Churchill and Roosevelt negotiated the [[Quebec Agreement]],{{sfn|Gowing|1964|pp=168–173}}{{sfn|Bernstein|1976|pp=216–217}} which established the [[Combined Policy Committee]] to coordinate the efforts of the US and UK; Canada was not a signatory, but the Agreement provided for a Canadian representative on the Combined Policy Committee in view of Canada's contribution to the effort.{{sfn|Jones|1985|p=296}} An agreement between Roosevelt and Churchill known as the [[Hyde Park Aide-Mémoire]], signed in late September 1944, extended the Quebec Agreement to the postwar period and suggested that "when a 'bomb' is finally available, it might perhaps, after mature consideration, be used against the Japanese, who should be warned that this bombardment will be repeated until they surrender".<ref>{{cite web|url=https://ahf.nuclearmuseum.org/ahf/key-documents/hyde-park-aide-memoire/|title=Hyde Park Aide-Mémoire (18 September 1944)|date=2022|publisher=Atomic Heritage Foundation}}</ref>{{sfnb|Gowing|1964|pp=340–342}}

When cooperation resumed after the Quebec Agreement, the Americans' progress and expenditures amazed the British. Chadwick pressed for British involvement in the Manhattan Project to the fullest extent and abandoned hopes of an independent British project during the war.{{r|fakley1983}} With Churchill's backing, he attempted to ensure that every request from Groves for assistance was honored.{{sfn|Gowing|1964|pp=242–244}} The British Mission that arrived in the United States in December 1943 included [[Niels Bohr]], Otto Frisch, [[Klaus Fuchs]], Rudolf Peierls, and [[Ernest William Titterton|Ernest Titterton]].{{sfn|Hunner|2004|p=26}} More scientists arrived in early 1944. While those assigned to gaseous diffusion left by the fall of 1944, the thirty-five working under Oliphant with Lawrence at Berkeley were assigned to existing laboratory groups and most stayed until the end of the war. The nineteen sent to Los Alamos also joined existing groups, primarily related to implosion and bomb assembly, but not the plutonium-related ones.{{r|fakley1983}} The Quebec Agreement specified that nuclear weapons would not be used against another country without the mutual consent of the US and UK. In June 1945, Wilson agreed that the nuclear bombing of Japan would be recorded as a decision of the Combined Policy Committee.{{sfn|Gowing|1964|p=372}}

The Combined Policy Committee created the [[Combined Development Trust]] in June 1944, with Groves as its chairman, to procure uranium and [[thorium#Occurrence|thorium ores]] on international markets. The [[Belgian Congo]] and Canada held much of the world's uranium outside Eastern Europe, and the [[Belgian Government in Exile]] was in London. Britain agreed to give the United States most of the Belgian ore, as it could not use most of the supply without restricted American research.{{sfn|Bernstein|1976|pp=223–224}} In 1944, the Trust purchased {{convert|3440000|lb|kg}} of uranium oxide ore from companies operating mines in the Belgian Congo. To avoid briefing US Secretary of the Treasury [[Henry Morgenthau Jr.]], a special account not subject to the usual auditing and controls was used to hold Trust monies. Between 1944 and his resignation from the Trust in 1947, Groves deposited a total of $37.5&nbsp;million.{{sfn|Jones|1985|pp=90, 299–306}}

Groves later said that the British scientists' direct contributions to the Manhattan Project were "helpful but not vital," but "there probably would have been no atomic bomb to drop on Hiroshima" without Britain's (particularly Churchill's) impetus.{{sfn|Groves|1962|p=408}} The British wartime participation was crucial to the success of their [[High Explosive Research|independent nuclear weapons program]] when the [[McMahon Act]] of 1946 temporarily ended American nuclear cooperation.{{r|fakley1983}}