Reportedly, Schellenberg and Wilhelm Canaris, the head of the "Abwehr", were friends. They would go horseback-riding together in Berlin's wooded Grunewald, where they discussed the future of Nazi Germany. Often present at these equestrian outings were Heydrich and Werner Best. Their alleged friendship aside, Canaris was careful around Schellenberg, a man whose ambitions included controlling all intelligence for the Reich. Like Heydrich, Schellenberg ultimately envisioned a centrally directed "all-embracing security system" and a singular "Greater German Intelligence Service" under direct Nazi control (unlike the "Abwehr", which was part of the Wehrmacht). Nonetheless, there are indications that Schellenberg preferred to deal with Canaris' "Abwehr" over the Gestapo, particularly since he distrusted its chief, Heinrich Müller. However, after the attempted assassination of Hitler on 20 July 1944, the "Abwehr" was dissolved and the SD was given additional powers over intelligence across the Reich. Canaris was arrested on 23 July 1944 on the basis of the interrogation of his successor at military intelligence, Georg Hansen.