 In January 1964, Mendenhall became director of the State Department's Vietnam Working Group and in July he became the director of the Office of Far Eastern Regional Affairs.In 1965, he was named director of the U.S. Agency for International Development (USAID) Mission in Laos, then the second largest such agency in the world.In 1968, he returned to Washington as deputy director, and later head of the USAID Vietnam Bureau.