 After his Army service, he received a master's degree in public administration from New York University in 1948.Nelson began working for the Mutual Security Administration (the forerunner of the U.S. Agency for International Development (USAID)) in the Philippines as Deputy Chief of the Rural Development Division from 1952 to 1958.After a short stint in Iran, he returned to the Philippines as Chief of the Community Development Division from 1958 to 1960.