Leibler, who obtained his PhD at U Illinois, worked in the National Security Agency with Kullback. Their 1951 paper introduced the eponymous Kullback-Leibler information measure. In 1958 he was appointed to the Institute for Defense Analysis, becoming its Director in 1963. In 1977 he was appointed Chief of the Office of Research at the National Security Agency.
http://www.nsa.gov/about/cryptologic_heritage/hall_of_honor/2002/leibler.shtml Obituary and photograph.