Oscar was drafted into the Army in 1942, but due to his special training he was assigned to the Special Engineer Detachment, a program that identified enlisted personnel with special technical or scientific skills, and put them to work on the Manhattan Project, the effort to build an atomic bomb. He was assigned to the Clinton Engineer Works in Oak Ridge, Tennessee, and then to the Los Alamos Laboratory in New Mexico. He was present at the Trinity nuclear test on July 16, 1945, with a group measuring the seismological effect of the explosion.
Post-war
Stuart was discharged from the Army in 1946, but continued to work for it in a civilian capacity with the Civil Affairs Division in Europe. He wrote a report on economic progress in Bizone, Germany in 1949, and one on the Army's education program the following year. Stuart's wife Miriam graduated from George Washington University Medical School that year, but when he applied for a job at the State Department, he was told that he would not be granted the necessary security clearance. Oscar applied for a civilian position at Los Alamos in 1947, but withdrew his application. Instead, he went to the University of Michigan, where he completed his master's degree in electrical engineering. After he graduated in August 1948, he took a job at the US Navy's Underwater Sound Laboratory in New London, Connecticut, where research on sonar for submarines was conducted. In August 1949, the commanding officer recommended his termination as a security risk, but on August 29 a review board overturned this decision. He was transferred to the Electronic Shore Division of the Bureau of Ships, where he was involved in the installation of electronic equipment in American and European harbors. The equipment itself was not secret, but the location of devices was. He was the only man working in the unit who did not hold a security clearance. On 1 June 1951 he tendered his resignation.
Emigration
On 3 July 1951, Stuart, Oscar, Miriam and Miriam's mother Anna boarded the liner bound for Le Havre. They then flew to Israel, where they visited Abraham and Jennie, who had re-emigrated in August 1950 and were living in Gan Yavne. They went to Vienna, and then to Moscow. Stuart and Oscar were employed there by the Soviet Academy of Sciences. Miriam and Stuart divorced in September 1961, and she returned to the United States in December 1969. She later worked as a medical technician at the United Nations until 1974. She died in 2002. Stuart and Oscar married Russian women. They became friends with Donald MacLean, who worked with them. Stuart published a couple of books on US Neocolonialism in Africa, which was translated into English, and Weaponry and Dollars: The Wellsprings of U.S. Foreign Policy, which was published only in Russian.
Discovery
American codebreakers working on Venona found that the Manhattan Project had been penetrated by Soviet spies, which gave it the codename "Enormous". They found references to codenames for three Soviet atomic spies working at Los Alamos: "M'Lad", who turned out to be Theodore Hall; "Caliber", who was David Greenglass; and "Godsend", who was ultimately identified as Oscar Seborer. Since Klaus Fuchs was also known to be a Soviet spy, there were at least four Soviet agents at Los Alamos.
