This was an Allied effort, largely by the USA and UK, around the end of World War II to investigate the German nuclear energy and nuclear weapon programmes, to seize German nuclear resources, materials and personnel to further US research and to prevent their capture by the Soviets, and to establish how far the Germans had gone toward the creation of an atomic weapon (spring/summer 1945).
The undertaking had its origins in an earlier effort, by a somewhat smaller team, despatched to Italy during 1943/44 to track down German teams, led by Werner Heisenberg, working on the possible development of atomic weapons. The limited success of this first undertaking paved the way for the somewhat larger ‘Alsos’, whose team included agents of the US Army’s Counter-Intelligence Corps and scientists of the US Office of Scientific Research and Development. The operation’s personnel followed immediately behind the Allied front-line forces, first into Italy, then into France and finally into Germany, with the primary task of looking for any relevant personnel, records, materials and sites.
The name of the operation is the Greek word for ‘grove’, and was thus a punning play on the name of the military director of the Manhattan Engineer District (cover designation of the ‘Manhattan’ Project), Major General Leslie M. Groves. This very able administrator was the driving force behind ‘Alsos’, in part as a result of his desire to make sure that German technology and personnel did not fall into Soviet hands, and thus to prolong for as long as possible the anticipated US monopoly of nuclear weapons.
The scientific and technical leader of ‘Alsos’ was Samuel Goudsmit, while its military leader was Lieutenant Colonel Boris Pash, formerly a ‘Manhattan’ Project security officer. The project managed to find and remove many of the German research effort’s personnel and also a comparatively large volume of the surviving records and equipment. Most of the senior research personnel, including Heisenberg, Otto Hahn and Carl Friedrich von Weizsäcker, were held at Farm Hall in England and for several months.
The ‘Alsos’ effort finally concluded that the Allies had completely overtaken the German atomic bomb effort by a time as early as 1942. Compared with the ‘Manhattan’ Project, which was one of the largest scientific efforts of all time, the German project was significantly underfunded and understaffed, and it is questionable if Germany would ever have had the resources or isolation required for the secret production of an atomic weapon.