'Soviet Alsos' or 'Russian Alsos' was the Western codename for a Soviet operation in Germany, Austria and Czechoslovakia in order to seize and exploit German atomic related facilities, intellectual materials, material resources, and scientific personnel for the benefit of the Soviet atomic bomb project (April 1945/1946).

Soviet scientists, aided greatly by Soviet espionage within the 'Manhattan Project', would have been able eventually to design and construct their first atomic bomb without any exploitation of German technology and scientists. However, the contributions of the German scientists is borne out by the many prizes and other awards given to them after the second Soviet second test, which was of a uranium-based atomic bomb: awards for uranium production and isotope separation featured highly in these awards. Also significant in both the first Soviet atomic bomb test (a plutonium-based device which required a uranium reactor for plutonium generation) and the second test was the Soviet acquisition of a significant amount of uranium immediately before and shortly after the end of World War II, a fact which the Soviets admitted had saved them a year.

Near the end of World War II in Europe and soon after it, the USSR and the Western powers launched programmes, such as the US 'Paperclip', to foster technology transfer and exploit German technical specialists. The USSR had so-called 'trophy brigades' advancing with their military forces. In the area of atomic technology, while the USA had 'Alsos' that was matched by the Soviet 'Osoaviakhim'. While operational aspects of the Soviet operation were modelled after the 'trophy brigades', a more refined approach was warranted for the exploitation of German atomic related facilities, intellectual materials and scientific personnel, and this led to a decree late in 1944 and the formation of specialised exploitation teams early in 1945. However, the 'Soviet Alsos' had broader objectives, which included wholesale relocation of scientific facilities to the Soviet Union.

On 18 September 1944, a decree established General Leytenant Avram P. Zavenyagin’s specialised task force within the NKVD’s 9^th Chief Directorate to support the work of German scientists 'invited' to the USSR.

On 23 March 1945, Commissar-General of State Security Lavrenti P. Beria, head of the NKVD, suggested that specialised teams be sent to Germany to search for atomic technology and personnel working on such technology. On the following day, he instructed Igor V. Kurchatov, head of Laboratory No. 2, to submit requirements on the formation of such teams for despatch to Germany, Austria and Czechoslovakia, and on the same day signed a directive appointing his deputy, Commissar of State Security 3^rd Rank Avram P. Zavenyagin, to head the operation to locate and deport German atomic scientists or any other specialists who could be of use to the Soviet atomic bomb project. Operational control of the teams was allocated to the SMERSH military counter-intelligence agency. Two members of Laboratory No. 2, Lev A. Artsimovich and Yuli B. Khariton, were assigned to provide scientific guidance to the operation. The whole scientific staff at Laboratory No. 2, the only Soviet atomic laboratory at that time, numbered less than 100 persons, and almost 40 of these were sent to Germany.

The Battle of Berlin was one of the last major engagements of World War II in Europe. Given the fact that most of the German scientific facilities were located in Berlin and its suburbs, this area became a major target of the search teams. Great speed was required as US forces were approaching Berlin rapidly. Soviet troops broke Berlin’s perimeter defences on 25 April, and the USSR announced the fall of the German capital on 2 May. The main search team, headed Zavenyagin, arrived in Berlin on 3 May, and included General Major of Technical-Engineering Service Vasili A. Makhnyov and the nuclear physicists Khariton, Isaak K. Kikoin, Lev A. Artsimovich and Georgi N. Flerov. of whom the last had arrived. The most important targets for the team included the Kaiser-Wilhelm Institut für Physik, the Freie Universität Berlin and the Technische Hochschule Berlin.

The search teams occupied an entire building large enough also to accommodate German scientists recovered by the team. Unfortunately for the Soviet effort, the Kaiser-Wilhelm Institut für Physik had for the most part been moved in 1943 and 1944 to Hechingen, on the edge of the Black Forest, which eventually became part of the French occupation zone: this and a little luck allowed the Americans to take into custody a large number of German scientists associated with nuclear research. The only section of the institute which remained in Berlin was the low-temperature physics section, headed by Ludwig Bewilogua, who was in charge of the exponential uranium pile.

Manfred von Ardenne (director of his Forschungslaboratorium für Elektronenphysik private laboratory in Berlin-Lichterfelde), Gustav Hertz (a Nobel laureate and director of the Siemens Research Laboratory II in Berlin-Siemensstadt), Peter Adolf Thiessen (professor at the Humboldt-Universität zu Berlin and director of the Kaiser-Wilhelm-Institut für physikalische Chemie und Elektrochemie in Berlin-Dahlem), and Max Volmer (professor and director of the Physical Chemistry Institute at the Technische Hochschule Berlin in Berlin-Charlottenburg) had by this time agreed that whichever of them made first contact with the Soviets would speak for the rest. There were three objects in the agreement: prevention of the plundering of their institutes, continuation of their work with minimal interruption, and protection of themselves against prosecution for any past political acts. Before the end of World War II, Thiessen, who was a member of the Nazi party, nevertheless had communist contacts, and on 27 April arrived at von Ardenne’s institute in an armoured vehicle with a Soviet army major who was also a leading chemist, and gave von Ardenne a protective letter.

von Ardenne’s institute was visited on 10 May by Makhnyov, accompanied by Artsimovich, Flerov, Kikoin and Migulin. At the end of the meeting, Makhnyov suggested that von Ardenne continue his work in the USSR, and von Ardenne agreed. On 19 May, Zavenyagin informed von Ardenne that the Soviet government had proposed that the German scientist take over a large technical-physical research institute and continue his work. Two days later, von Ardenne, his wife, his father-in-law, his secretary and the biologist Wilhelm Menke were flown to Moscow. Soon after this, the rest of von Ardenne’s family and the contents of his laboratory were also transported to the USSR.

In its early stages, the Soviet atomic bomb project was in critical need of uranium. In May 1945, the sole atomic laboratory, Laboratory No. 2, had only seven tons of uranium oxide available to it. The critical nature of the laboratory’s stock can be realized when compared to the amounts needed for their first uranium reactor F-1 and their first plutonium production Reactor A in the Ural mountains: the first load of F-1 required 46 tons and the first load of Reactor A required 150 tons.

The Soviet search teams deployed to Germany, Austria and Czechoslovakia were fully aware of the Soviet need for uranium. However, Major General Leslie Groves, director of the 'Manhattan Project', was also aware of the requirement of uranium for his own effort and that of the Soviet atomic bomb project. Grove therefore arranged for the US 'Alsos' team to arrange for the removal of 1,200 tons of uranium ore from a salt mine near Stassfurt, an area due to fall within the Soviet occupation zone. This was later found to have been the bulk of the German stock of uranium ore.

As soon as the Soviets occupied Vienna, a search team was sent to Austria. Vladimir Shevchenko, director of Scientific Research Institute No. 9, and the atomic scientist Igor N. Golovin from Laboratory No. 2 remained in Vienna from 13 April to 10 May, and here interviewed scientists from the Radium Institute of the Academy of Sciences and from the Second Physical Institute of the University of Vienna. Information collected provided an overview of German organisations involved in the uranium project, including companies potentially engaged in metallic uranium production. In an Auergesellschaft building in Vienna, they retrieved 750 lb (340 kg) of metallic uranium, a precursor to what would be found in Germany, as indeed Auergesellschaft was a main producer.

The Auergesellschaft facility in Oranienburg had nearly 100 tonnes of fairly pure uranium oxide, and a search team located this. The Americans had bombed the facility near the end of the war to deny the works to the Soviets. The USSR seized this uranium as reparations, and this quantity amounted to between 25% and 40% of the uranium taken from Germany and Czechoslovakia at the end of the war. Khariton later said that the uranium found there saved the USSR one year in its atomic bomb project.

Not knowing about the find in Oranienburg, Khariton and Kikoin began their own intensive search. From their inspection of a plant in the Grunau district, they learned that the company Rohes had shipped several hundred tons of uranium, but were unable to establish the final destination. While in Potsdam, they determined the name of the head of the Belgian office of Rohes, and the services of SMERSH military counter-intelligence agency were used to find and seize this man and deliver him to the two physicists. Under questioning by SMERSH, the man revealed that the uranium was in Neustadt. There are some 20 towns in Germany with that name, and 10 of these were in the Soviet zone of occupation, and in Neustadt-Glewe they found more than 100 tons of uranium oxide.