 He stayed at Kentucky until 1946, apart from between 1943 and 1945, during which he did war service for the Ballistic Research Laboratory at the Aberdeen Proving Ground, Maryland.In 1946 he moved to New York University, where he remained for the rest of his career.Throughout the 1940s and 1950s he continued to work on the Radon transform, in particular its application to linear partial differential equations, convex geometry, and the mathematical theory of water waves.