After work with the Surry Players at the Mercury Theatre in New York he join the US Army Air Forces during World War II becoming a division chief in the Strategic Bombing Survey of the War Department. He married and joined the United States Department of State in 1946 as a research assistant becoming chief of the Far East political section then deputy director of the Office of Intelligence Research. Commissioned as a Foreign Service Officer in 1955 he was posted as deputy director of the Research Center of the South East Asia Treaty Organization to Bangkok. In 1958 he was assigned to Surabaya with responsibility for Portuguese Timor until appointed counselor for economic affairs to Jakarta (Indonesia) in 1960. After attending the Senior Seminar in 1961-1962, he appointed deputy chief of mission to Canberra (Australia) 1963. He returned to Jakarta in 1965 as DCM with the personal rank of minister. On 15 September 1969 President Richard Nixon appointed Lydman as Ambassador to Malaysia, serving in Kuala Lumpur until he retired on 20 December 1974.