After the war Ley returned to university, gaining a doctorate in 1920. He was employed as a food chemist by a branch of the giant IG Farben company, based in Leverkusen in the Ruhr. Enraged by the French occupation of the Ruhr in 1924, Ley became an ultra-nationalist and joined the Nazi Party soon after reading Adolf Hitler's speech at his trial following the Beer Hall Putsch in Munich.