Aaron held government service positions from 1961 to 1981 and again from 1993 to 2000, beginning in the Foreign Service where he worked with NATO and negotiated nuclear arms reductions. After leaving the Foreign Service he went on to serve on the Senate staff of Walter F. Mondale, as task force director for the Senate Intelligence Committee, and as Deputy National Security Advisor to President Jimmy Carter. Aaron was also a confidential presidential emissary to Europe, the Middle East, Africa, Latin America and Asia in the Carter Administration. In his role as Middle East emissary, Aaron helped set up the negotiations for the Camp David accords between Israel and Egypt in 1978. During the Clinton administration, Aaron served as U.S. permanent representative to the Organization for Economic Cooperation and Development, special White House envoy for cryptography, and undersecretary of Commerce for international trade. In the private sector, Aaron held senior positions at Oppenheimer & Co., a financial services firm, from 1981 to 1993. After leaving government service in 2000 he became a senior international advisor to Dorsey & Whitney, a law firm. Aaron has served as a member of the Council on Foreign Relations, the Board of the Atlantic Council, and on the Steering Committee for Homeland Security. In addition, Aaron has written three novels, and was the writer of a documentary on Operation Desert Storm, "The Lessons of War." He holds a master's degree in public administration from Princeton University, and was awarded the National Defense Medal in 1981.