The first important biographer is Konrad Heiden, who wrote a biography while Hitler was still alive. It was the first comprehensive and critical work that a German author was able to write without censorship, as he fled into exile immediately after the Nazis came to power in 1933.

As a Social Democratic journalist, he had been writing about the Munich right-wing extremist political scene since his early twenties. He soon became the leading expert and a staunch opponent of the Nazi movement and Adolf Hitler. In addition, he was of Jewish descent on his mother's side, so he had two reasons for leaving the country.