This paper summarizes the evolution of the tank in the US Army during the period 1919-1940. It examines the US Army's post World War I concept of future war and explores the evolution of tank design, force organization, and mechanized doctrine through the interwar period. The issues and factors that were crucial to the early evolution of the tank in the US Army were largely responsible for the role the tank played during and after World War II. This suggests that the 1920s and 1930s were the most important period in the history of the tank. Although some conclusions can be drawn from this brief summary, they should remain tentative pending full treatment of the subject.