He was born the third of three sons in Jettingen in Swabia near Ulm to one of the oldest and most distinguished aristocratic South German Catholic families. Among his ancestors were several famous Prussians, including most notably August von Gneisenau. His name points to the imperial Stauffen Berg mountain and castle. Stauffenberg was very well educated and was inclined to literature but eventually took up a military career. In 1926 he joined the family regiment in Bamberg, the Reiter- und Kavallerieregiment 17 (17th Cavalry Regiment). In 1933 Adolf Hitler came to power and while some aspects of the party were repugnant to him, he was not initially in complete opposition to their ideas, especially in the area of nationalism. However after Kristallnacht in November 1938 he felt that great shame had been brought upon Germany and it had deeply offended his sense of morality and justice. The treatment of the Jews and the suppression of religion in Germany made Stauffenberg more and more an opponent of the Nazis.
In the military, he had worked his way through the grades and on 1 January 1937 he was promoted to Hauptmann, a rank he would hold for the next six years. His regiment became part of the Sixth Panzer Division and was involved in the occupation of the Sudetenland and, once war broke out, in the Polish, French and Russian campaigns. Towards the end of the French campaign (31 May 1940) he was awarded the Iron Cross First Class.
On 1 January 1943 he was promoted to Oberstleutnant and was soon transferred to the North African campaign. There while he was scouting out a new command area his vehicle was strafed by marauding Allied fighter-bombers and he was severely wounded. He spent three months in hospital and ended up losing his left eye, his right hand and the fourth and fifth fingers of his left hand - though he later joked that he hardly knew what he had done with all ten fingers when he had them.
While his uncle, Graf Niklaus von Üxküll, approached him to join the resistance movement after the Polish campaign in 1939, it was Stauffenberg's individual conscience and his religious convictions that urged him to act. Initially he felt powerless as he was in no position of authority to help organise a coup, but finally in 1943 after recuperating from his wounds he was posted as a staff officer to the Replacement Army located in an office on the Bendlerstrasse in Berlin. Here, one of his superiors was General Friedrich Olbricht, a committed member of the resistance movement. In the Replacement Army they had a unique opportunity to launch a coup as one of its functions was to have "Operation Valkyrie" in place - a contingency measure to which would let the Replacement Army assume control of the Reich in the event of internal disturbances where communications with the military high command were blocked. Ironically, this plan had been agreed to by Hitler and was now secretly to become the means of sweeping him from power.
While Stauffenberg's part in the plan required him to be at the Bendlerstrasse office to telephone regular Army units from around the Reich to arrest leaders of political organisations such as the Sicherheitsdienst and the Gestapo, in the end Stauffenberg was the only one of the conspirators who had regular access to Hitler, at his briefing meetings. Even with only three fingers remaining, Stauffenberg, in 1944 now promoted to Oberst, agreed to carry out the assassination of the German Führer Adolf Hitler himself. The attempt took place at the Führer's briefing hut at the military high command in Rastenburg, East Prussia on July 20, 1944. Von Stauffenberg's briefcase was packed with explosives and a simple ten to fifteen minute timer set. He entered the briefing room where Hitler was present, placed the briefcase under the table and then quickly left the room unnoticed. From a nearby shelter he waited until the explosion tore through the hut and from what he saw, he was convinced that no one could have survived such a blast. He and his aide de camp, Leutnant Werner von Haeften, quickly walked away and talked their way out of the heavily guarded compound to fly back to Berlin in a waiting Heinkel He 111. While in transit, an order was issued from the Führer's headquarters to shoot them down, but the order landed on the desk of a fellow-conspirator, Friedrich Georgi of the air staff, and was not passed on.
Hitler survived the attempt on his life and once he broadcast a message on the state radio it became obvious that the coup attempt had failed. Shortly afterwards the conspirators were overpowered in their Bendlerstrasse office, with Stauffenberg being shot in the shoulder.
General Friedrich Fromm, Commander-in-Chief of the Replacement Army and himself a suspected conspirator who was later executed, held an impromptu court martial and condemned the ringleaders of the conspiracy to death. Stauffenberg along with fellow officers General Olbricht, Leutnant von Haeften and Oberst Albrecht Mertz von Quirnheim were later shot that night by firing squad in the courtyard of the Bendler-Block (War Ministry). As his turn came, Stauffenberg spoke his last words: 'Es lebe unser geheimes Deutschland!' ('Long live our secret Germany!') His eldest brother Berthold, another central figure in the plot was executed later.
Today Claus von Stauffenberg is celebrated as a hero and symbol of the German resistance to the Nazi regime. Since the war the Bendler-Block has become a memorial to the failed anti-Nazi resistance movement. The street's name was ceremonially changed from "Bendlerstrasse" to "Stauffenbergstrasse" and the Bendler-Block now houses a permanent exhibition with more than 5,000 photographs and documents showing the various resistance organisations at work during the Hitler era. The courtyard where the officers were shot is now a site of remembrance with a plaque commemorating the events and a memorial bronze figure of a young man with his hands symbolically bound.