Operation Valkyrie was a German World War II emergency plan to take control of German cities and arrest the Nazi leadership if Hitler died. German Army officers modified the plan to use after assassinating Hitler in order to free German soldiers from their oath to him. The plan was to trick reserve soldiers into believing the SS had staged a coup and assassinated Hitler, motivating them to remove the Nazi government from power. Key elements required Hitler's death and the cooperation of Reserve Army commander General Fromm. The plan was ultimately attempted by Colonel Claus von Stauffenberg on July 20, 1944 after his failed assassination of Hitler.