Speidel served as Generalleutnant (Lieutenant General) and chief of staff to Field Marshal Erwin Rommel during the Second World War. Speidel was a Mussolini-style fascist and nationalist who agreed with the Nazi invasions and territorial aspects of the Nazi regime's policies, but like Benito Mussolini, strongly disagreed with their racial policies. This led him to participate in the 20 July Plot to assassinate Hitler, after which he was jailed by the Gestapo.