John Lansdale Jr. (9 January 1912 – 22 August 2003) was a United States Army colonel who was in charge of intelligence and security for the Manhattan Project.
A graduate of the Virginia Military Institute and Harvard Law School, Lansdale was commissioned as a second lieutenant in the United States Army Reserve in 1933. He was called up for active duty in June 1941, and was assigned to the Investigations Branch in the Office of the Assistant Chief of Staff, G-2 (military intelligence) of the War Department General Staff. He became involved with the Manhattan Project in 1942, eventually becoming Brigadier General Leslie Groves‘s special assistant for security. Lansdale coordinated the activities of the Manhattan Project’s field security teams with those of other agencies such as the FBI.
In April 1945, Groves sent Lansdale to Europe, where he worked with the Alsos Mission to secure 1,000 tons of uranium ore from the German Wirtschaftliche Forschungsgesellschaft(WiFO) plant in Stassfurt. He also participated in the planning and execution of Operation Harborage, in which a special Allied force went deep behind enemy lines, seized 1.5 tons of uranium ingots, and captured a number of German nuclear energy project scientists, including Carl Friedrich von Weizsäcker, Max von Laue, Karl Wirtz, Horst Korsching and Erich Bagge and Otto Hahn.