Colonel Claus Graf Schenk von Stauffenberg (1907-1944) was central to the planning and execution of the July 20th plot, the most wide-ranging conspiracy against the Nazi regime. Like many other military men, he had initially approved the Nazis' nationalistic and militaristic goals. But Hitler's criminal and increasingly incompetent approach to conducting the war led Stauffenberg to turn away from the Nazi regime. After being seriously wounded in fighting North Africa in April 1943, Stauffenberg held a series of posts in the Wehrmacht administration and used these positions to forge contacts with various military and civilian resistance groups, including the Kreisau Circle. Over time, Stauffenberg became increasingly convinced that he would have to help destroy the Nazi regime in order to save Germany from an impending military catastrophe. Together with other high-ranking officers, he reworked the Replacement Army’s operational plan for suppressing domestic unrest and transformed it into a plan for a coup d'état – “Operation Valkyrie.” According to the plan, once Hitler had been killed, the Replacement Army would eliminate the most important authorities of the Nazi regime through the mass arrest of high-ranking members of the NSDAP, the Gestapo, the SS, and the SD, and take executive power into its own hands. Additionally, the plan called for Stauffenberg and his co-conspirators to take complete control of communications by occupying all radio transmitters and stations.

Stauffenberg himself played a critical double role in the plot, insofar as he was involved in both the assassination attempt and the subsequent coup d'état. As chief of staff to the commander of the Replacement Army, he had direct access to Hitler during discussions of the military situation at the "Wolf's Lair," the Führer's East Prussian headquarters. After numerous postponements, the conspirators decided to assassinate Hitler during one such discussion on July 20, 1944. Stauffenberg detonated a bomb in the headquarters and rushed off to Berlin, thinking he had killed Hitler. Because there was no official report of Hitler's death, the corresponding coup d'état got off to a delayed and shaky start. The Nazi leadership immediately initiated effective counter-measures and destroyed the attempted putsch within a short time. Stauffenberg was arrested and shot the same night.