The Nationalists returned to focus on the capture of northern Spain. German test aircraft, with the latest models, faced an outdated Basque section ("Escuadrilla vasca") of the Spanish Republican Air Force. Heavy aerial bombardment from 200 Nationalist, German and Italian aircraft was used far behind Basque lines in August 1937, leading to the fall of Santander after the Battle of Santander on 1 September. The formal battle in Asturias ended with the fall of Gijón on 21 October. Germany immediately began to ship the products of the region's industry back to Germany. Sperrle argued repeatedly with Faupel, and against HISMA's monopoly. Faupel was replaced with Eberhard von Stohrer by Franco, through Sperrle. Sperrle also returned to Germany and was replaced by Helmuth Volkmann; following disagreements with Volkmann, Von Richthofen would be replaced with Hermann Plocher in early 1938.