He headed the Secret Intelligence Branch of the Office of Strategic Services during World War II.
[3] Shepardson's involvement in international relations began when sent to the 1919 Paris Peace Conference by the State Department as an aide to Edward M. House, where he became secretary to the commission responsible for drafting the Covenant of the League of Nations.
From 1920, he wrote for the Round Table, a British journal edited by former Beit Lecturer in Colonial History, Lionel Curtis.
Gray and Co.[5] Between 1925 and 1927 he served as a director on John D. Rockefeller's General Education Board, specialising in the development of agricultural and biological research.
He was vice-president of International Railways of Central America, a transport arm of the United Fruit Company, from 1931 until 1942.