By September 1943, Quirnheim had become involved in the plot to assassinate Hitler. He, his superior General Friedrich Olbricht and Stauffenberg planned Operation Valkyrie, a plan of action to be implemented as soon as Hitler had been killed. Meanwhile, Quirnheim succeeded Stauffenberg as Chief of Staff at the Army's General Office in Berlin. Immediately after the attempt on Hitler's life in East Prussia on 20 July 1944, Quirnheim urged General Olbricht to activate Operation Valkyrie, even though they could not be sure whether Hitler was dead. At about the same time, however, news began to arrive that Hitler had survived the assassination attempt.