Later, he served as the first United States Arms Control and Disarmament Agency director, under Presidents John F. Kennedy and Lyndon B. Johnson.

Born in Westfield, New Jersey in 1897, Foster attended the Massachusetts Institute of Technology (MIT), studying chemical engineering.

[2] When President Harry Truman launched the Marshall Plan for that purpose in 1948, Harriman became the Special Representative of the effort in Europe and Foster became his deputy.

In 1953, upon deciding to leave his role in the government, Foster accepted the position of President of the prestigious Manufacturing Chemists Association (MCA).

[2] During his time there, he proposed a national-level air pollution abatement committee, which eventually led to offices within the government prior to the creation of the Environmental Protection Agency.

[2] In 1961, Foster worked with the Kennedy administration to pass a law creating a new Arms Control and Disarmament Agency, and served as its founding director (1961–1968).