The Manhattan Project begins

On 18 June 1942 the Chief of the US Army Corps of Engineers, Major General Eugene Reybold, summoned to Washington Colonel James C. Marshall, until then head of the engineer district in Syracuse, New York, and instructed him to organise the military side of the programme to build an atomic bomb. Marshall, a construction engineer, had never heard of nuclear fission. He read the report that scientists had submitted to the President a few days earlier, and years later he recalled: “I spent a sleepless night trying to understand what it was all about. I had never heard of fission, but I knew that you could not build one decent plant for ninety million dollars, let alone four.”

War chronologies give this day as the beginning of the Manhattan Project. That is a simplification, but a justified one. American research on uranium had been under way since the autumn of 1939, and the name “Manhattan” did not appear until August 1942. Yet it was precisely in mid-June 1942 that the programme passed from the hands of civilian scientists into those of the Army, and from the laboratory stage to the construction of huge industrial plants. It is also true that the project drew on earlier British work: without the British calculations of 1940–1941 the Americans would have started many months later.

From Einstein’s letter to the MAUD Report

The first impulse came from scientists who had fled Europe to escape Hitler. In August 1939 Leó Szilárd wrote, and Albert Einstein signed, a letter to President Franklin Delano Roosevelt warning that the fission of uranium, confirmed in January 1939 also at Columbia University, could be used to build bombs of a new type and that Germany might be working on them. The President set up an Advisory Committee on Uranium under Lyman Briggs, director of the National Bureau of Standards. The committee, however, worked slowly and cautiously, had only modest funds at its disposal, and the military did not take the matter seriously. In June 1940 its work was taken over by the new National Defense Research Committee (NDRC), and in June 1941 by the Office of Scientific Research and Development (OSRD), headed by the engineer Vannevar Bush. His deputy and chairman of the NDRC was the chemist and President of Harvard University, James Bryant Conant.

The breakthrough came from Britain. In March 1940 two refugees from the Reich working in Birmingham, Otto Frisch and Rudolf Peierls, calculated in a short memorandum that a nuclear explosion would require not several tonnes of uranium, as had been thought, but a few kilograms of the pure isotope uranium-235, and that an aircraft could carry such a bomb. The British government set up a committee of scientists known by the codename MAUD. In July 1941 the committee concluded unanimously that a uranium bomb could be built during the present war and recommended that the effort be made regardless of cost. Britain launched its own programme under the deliberately misleading codename Tube Alloys, supervised by the Lord President of the Council, John Anderson.

The MAUD Report reached the Americans through the channels of scientific exchange opened in 1940 by the Tizard Mission. Briggs, however, locked it in his safe and did not show it to the members of his committee. At the end of August 1941 the Australian physicist Mark Oliphant, a member of the MAUD Committee, flew to the United States and, astonished that his American colleagues knew nothing of the British conclusions, won over first Ernest Lawrence at Berkeley and, through him, Conant and Arthur Compton.

The President’s decisions

On 9 October 1941, two months before Pearl Harbor, Bush presented the British conclusions to Roosevelt. The President agreed to speed up the work and set up a small Top Policy Group: Vice-President Henry Wallace, the Secretary of War, Henry Stimson, the Army Chief of Staff, General George Marshall (no relation of the colonel), Bush and Conant. He also decided that when the time came to build, the Army rather than the Navy would take charge, as it had greater experience of large construction projects. On 11 October he proposed atomic co-operation to Winston Churchill. Churchill did not reply until December, and then only in general terms: the British, at that time further ahead, were worried about the security of the American programme and did not want a joint enterprise.

The war, which the United States entered in December 1941, opened the coffers. On 19 January 1942 Roosevelt approved Bush’s plan in a short note, which he sent back with instructions that Bush keep it in his own safe. In March he wrote that the whole thing should be pushed forward, since time was “very much of the essence”. Compton concentrated work on the reactor at the Metallurgical Laboratory of the University of Chicago, where Enrico Fermi’s team was preparing the first atomic pile. No one yet knew which of the routes to fissile material would prove effective: separating the isotopes of uranium electromagnetically (Lawrence), by gaseous diffusion or in centrifuges, or producing a new element, plutonium, in a reactor. The scientists’ committee recommended pursuing all of them at once.

On 13 June 1942 Bush and Conant presented to the Vice-President, Stimson and General Marshall a report with a plan for fiscal year 1943: about 90 million dollars, of which 54 million was for construction carried out by the Corps of Engineers, 31 million for OSRD research and 5 million in reserve. They justified the haste by the fear that Germany would build the bomb first. On 17 June Roosevelt approved the report, writing “OK FDR” on it. The next day Reybold appointed Colonel Marshall.

The Army takes over the programme

Marshall was to build the plants, while civilian scientists were to carry on the research. On 19 June Bush abolished the large uranium section of the OSRD (S-1) and replaced it with a small S-1 Executive Committee under Conant, with Briggs, Compton, Lawrence, the chemist Eger Murphree and the Nobel laureate Harold Urey. Its first meeting, on 25 June, was already attended by Marshall and his deputy, Lieutenant Colonel Kenneth Nichols. They discussed buying land for the plants near Knoxville, Tennessee, where a state-owned hydroelectric system could supply enormous amounts of electricity, and choosing the firm Stone & Webster as the main contractor. On 30 June Marshall and Nichols inspected the land along the Clinch River.

Marshall set up his headquarters on the 18th floor of an office building at 270 Broadway in New York, close to the offices of Stone & Webster and to Columbia University. The programme was called “Development of Substitute Materials”. Colonel Leslie Groves, deputy chief of the construction division of the Corps of Engineers, considered that such a name merely aroused curiosity. Since engineer districts were named after the cities in which they had their headquarters, the new district, which had no territorial boundaries, was named the Manhattan Engineer District on 13 August 1942 (16 August according to some sources). In time the name of the district passed to the whole programme.

The first months were not a success. Marshall was conscientious but cautious: he held off buying the land in Tennessee until the results of the reactor experiments were known, and obtained for the project only an AA-3 priority rating, the same as an ordinary TNT factory. Bush complained to Stimson and the President about the slow pace. On 17 September 1942 Groves, soon promoted to brigadier general, took charge of the whole programme. Two days later he bought the site in Tennessee where the secret town of Oak Ridge grew up, and secured the highest priority. Marshall remained head of the district, under Groves, until August 1943.

The British and the Americans

June 1942 was a turning point for atomic co-operation in both senses. On the same 18 June that Marshall received his orders, Churchill flew into Washington. On 20 June at Hyde Park, Roosevelt’s family estate on the Hudson, the two leaders discussed Tube Alloys. According to Churchill’s memoirs, they agreed that the two countries would pool their information, work as equal partners and share the results, and that the large plants would be built in America, out of reach of German bombers. On the American side the conversation left no record whatever.

These arrangements soon lost their meaning. In 1941 the British had been ahead of the Americans, but with the enormous demands of the war they lacked the money, the manpower and the raw materials to build isotope separation plants. From mid-1942 the Americans pulled ahead ever faster, and the Army, which had taken over the programme, tightened secrecy and restricted the exchange of information. On 30 July Anderson warned Churchill that Britain’s pioneering work was “a dwindling asset” and that unless it was exploited quickly they would be left behind. In December 1942 Roosevelt agreed that the British should be given only what they could use during the war. Only the Quebec Agreement of 19 August 1943 merged the two programmes and sent British scientists to America.

The Germany that gave up

The American haste sprang from fear of Hitler’s bomb. The Americans did not know that at the same time Germany was giving it up. As early as the beginning of 1942 the Army Ordnance Office had concluded that an atomic weapon would not be ready in time to decide the war, and handed most of the work over to the civilian Reich Research Council. On 4 June 1942, two weeks before Marshall’s orders, at Harnack House in Berlin the physicist Werner Heisenberg briefed the Armaments Minister, Albert Speer, on the state of research. He said that a bomb was theoretically possible but that building one would take years. Speer granted modest sums for further research and concentrated the effort on weapons that could produce results more quickly. The German programme, run by the scientists of the so-called Uranverein (Uranium Club), never got beyond reactor experiments before the end of the war.

Place in the war

The order of 18 June 1942 opened the way to the greatest scientific and industrial undertaking of the war. On 2 December 1942 in Chicago Fermi’s team started up the first nuclear reactor, Chicago Pile-1. In 1943 came the plants at Oak Ridge, the reactor complex at Hanford in Washington State and the weapons design laboratory at Los Alamos in New Mexico under Robert Oppenheimer. The project cost about 2 billion dollars and at its peak employed more than a hundred thousand people, almost none of whom knew what they were working on. The secret was not kept from an ally: Soviet intelligence had informants in the project, among them the physicist Klaus Fuchs of the British mission.

On 16 July 1945 the first atomic bomb exploded in the New Mexico desert, and on 6 and 9 August 1945 the Americans dropped bombs on Hiroshima and Nagasaki. A weapon begun out of fear of Germany was used against Japan, and after the war it became the foundation of great-power rivalry. A programme which in June 1942 comprised a few university laboratories and a budget of some 90 million dollars changed the nature of war and of international politics in less than three years.