Oscar J. Vago was a Hungarian-born structural and civil engineer who became embroiled in the U.S. government's espionage investigations as the Cold War unfolded at the close of World War II. Vago briefly had a professional partnership with Abraham Brothman. Brothman owned a chemical engineering company in Long Island City that employed Harry Gold, who later declared himself an atomic spy and was a key witness against Julius and Ethel Rosenberg. Brothman was convicted in 1950 of conspiracy to impede a grand jury investigation and for conspiring with his secretary Miriam Moskowitz and Harry Gold to obstruct justice.

Vago, who was Jewish, had emigrated from Hungary to the U.S. in 1925 with a student visa, but overstayed the visa's time limit. After he married Hungarian emigre Claire Weiszmann, who became a U.S. citizen, the couple visited Hungary in 1932-1933 and Vago was able to return to the U.S. under an immigrant visa. He subsequently became a U.S. citizen. In 1950 he was questioned by the FBI and then subpoenaed to testify before a grand jury. Questioned, without an attorney present, about the date of his immigration to the U.S., he gave the later date. After consulting an attorney, he returned to the grand jury one week later and asked to correct his earlier testimony. His request was denied. In September 1950 he was indicted for perjury with a $50,000 bail. He was imprisoned at the Federal House of Detention in New York City until January 1951, when his family was able to get the bail reduced and raise the necessary funds. In the media Vago was portrayed as a missing link in the so-called Russian atom spy ring, and—-because of his Hungarian Jewish background/heritage—-was treated with suspicion in the media and courtroom. Finally, in June 1952, Vago was declared guilty by judge Sylvester Ryan following a brief trial without a jury. Ryan sentenced him to three years' probation, in a highly political sentencing statement. He noted that Vago had no ill intent in misstating the date of his arrival in the U.S., but based his guilty verdict on Vago's assumed Communist affiliation and Hungarian heritage.