Jacobson was working as a high school teacher in Detroit when, in the fall of 1932, he was recruited to work for the Soviet Military Intelligence (GRU) by the Comintern agent "Mrs. Morton", a pseudonym of Aino Kuusinen, the wife of the Finnish communist leader Otto Kuusinen.
He traveled to New York where the fledgling GRU agent Whittaker Chambers was assigned the task of meeting Jacobson and making a fitness report. Chambers advised against Jacobson's use as an underground agent because of his truculent temperament and the fact that he was missing fingers on one hand.
Nevertheless, the GRU sent him to Europe as part of an apparatus of Soviet agents, led by the wife of Alfred Tilton, that operated in Finland. The Finnish police uncovered the group after a suspected Army Officer fled to the Soviet Union with military secrets. Jacobson was arrested in October 1933, along with his wife, and he promptly confessed to his role as an agent and revealed the existence of another Soviet apparatus working in Paris which included Lydia Stahl and Robert Gordon Switz.
After a secret trial, the Finnish court sentenced Jacobson to six years imprisonment in April 1934. He was subsequently pardoned in July 1935 and returned to the United States.
- Chambers, Whittaker (1952). Witness. Random House. ISBN 0-89526-571-0.
- John Earl Haynes and Harvey Klehr, Venona: Decoding Soviet Espionage in America, Yale University Press (1999), pgs. 375, 469.
- Aino Kuusinen, The Rings of Destiny: Inside Soviet Russia from Lenin to Brezhnev, Morrow, 1974.
- Allen Weinstein, Perjury: The Hiss–Chambers Case, New York: Random House, (1997), pg. 106