Cairncross had given the Soviet Union a copy of the MAUD Committee report. Although not conveyed to the Americans, the British had other concerns about what might happen after the war if the Americans embraced isolationism, as had occurred after the First World War, and Britain had to fight the Soviet Union alone. The opportunity for a joint project was therefore missed. British and American exchange of information continued but their programmes remained separate. The Japanese attack on Pearl Harbor on 7 December 1941 led to the United States' entry into the war. Funding now became available in amounts undreamt of the year before. OSRD contracts were due to expire at the end of June 1942, and there was intense wartime competition for raw materials. It was agreed that in 1942–1943, the United States Army would fund $53 million of an $85 million programme. On 18 June 1942, Colonel James C. Marshall was ordered to organise the Army component. He established his headquarters on the 18th floor of 270 Broadway in New York City, with the innocuous name of the Manhattan Engineer District, following the usual practice of naming engineer districts after the city in which its headquarters was located. The project soon adopted the name "Manhattan" as well. By September 1942, Bush and Conant felt that the time had come for the Army to take over, something already approved by the president on 17 June 1942, and Brigadier General Leslie R. Groves, Jr. became the director of the Manhattan Project on 23 September 1942. Groves attempted to tighten security through a policy of strict compartmentalisation similar to the one that the British had imposed on radar. The American effort soon overtook the British. British scientists who visited the United States in 1942 were astounded at the progress and momentum the Manhattan Project had assumed. On 30 July 1942, Anderson advised Churchill that: "We must face the fact that ... [our] pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger'. Soon we shall have little or none". But Bush and Conant had already decided that British help was no longer needed. In October 1942, they convinced Roosevelt that the United States should independently develop the atomic bomb, despite the agreement of unrestricted scientific interchange between the US and Britain. The