He worked for the United States government from 1935 to 1975, first as an economist, then on the mobilization of the U.S. economy for World War II and finally as a diplomat both domestically and abroad.

On November 4, Martin traveled to Hakone, Kanagawa, as principal adviser to Secretary of State Dean Rusk and as chief of the U.S. Delegation at the meeting of the Joint United States-Japan Committee on Trade and Economic Affairs.

In March 1962,[2] President John F. Kennedy appointed Martin as Assistant Secretary of State for Inter-American Affairs, a position he held until January 2, 1964.

In that post, he helped direct new Kennedy administration policies toward Latin America, including managing U.S. involvement in the Alliance for Progress.

In May 1963, he headed the U.S. delegation to a meeting of the United Nations Economic Commission for Latin America in Mar del Plata, Argentina.

He then acted as Alternate U.S. Representative to the Inter-American Economic and Social Council Conference at the Ministerial Level in Sao Paulo, Brazil in November.

From 1975 to 1978, Martin served as Chairman of the Consultative Group on Food Production in Developing Countries at the World Bank.