Gregor Strasser
On 27 February 1933 the Reichstag fire occurred and Diels was the main interrogator of the principal accused, Marinus van der Lubbe. He told Hitler he thought that the fire was set by this single man. However, Hitler was convinced it was the Communists. Diels also ordered Arthur Nebe to arrange the killing of Gregor Strasser in October 1933; Strasser was later killed during the Night of the Long Knives in which Diels himself was almost killed.