At the Rockefeller Foundation, he was responsible for approving grants for major projects in molecular engineering and genetics, in agriculture (particularly for developing new strains of wheat and rice), and in medical research. During World War II, he was seconded from the foundation to head the Applied Mathematics Panel at the U.S. Office of Scientific Research and Development, directing the work of mathematicians in operations research with the assistance of Mina Rees. He was familiar with the development of electronic calculating machines and the successful application of mathematical and statistical techniques in cryptography.