Karl Haushofer
The Heartland Theory was enthusiastically taken up by the German school of Geopolitik, in particular by its main proponent Karl Haushofer. Geopolitik was later embraced by the German Nazi regime in the 1930s. The German interpretation of the Heartland Theory is referred to explicitly (without mentioning the connection to Mackinder) in "The Nazis Strike", the second of Frank Capra's "Why We Fight" series of American World War II propaganda films.