"Dr. Donald H. Menzel is well known for his work in astronomy, but his cryptologic work has never received a thorough review. The present article describes how his interest in this area was first sparked and provides the details of the secret class he led in “Naval Communications” (really cryptanalysis) at Radcliffe College during World War II. This class served as a prototype and was copied elsewhere. A sketch of some of the classified work he carried out during the war, and after, as a consultant, is also included, along with a brief overview of Menzel's personality and other interests."