On 1 May 1936, Trautloft was posted to "Jagdgeschwader" 134 "Horst Wessel" (JG 134—134th Fighter Wing), named after the Nazi martyr Horst Wessel. At the time of the outbreak of the Spanish Civil War, Trautloft was serving in the 9. "Staffel" (9th squadron) of JG 134. This squadron was subordinated to III. "Gruppe" of JG 134 and was commanded by "Major" Oskar Dinort. The "Gruppe" had been moved to an airfield at Cologne-Butzweilerhof on 9 March 1936 following the Remilitarization of the Rhineland. There on 28 July, Dinort called Trautloft and informed him of the unfolding events in Spain and Trautloft proactively volunteered for service in Spain.