At the end of 1943 the Schutz Staffeinel (SS) and the Gestapo managed to arrest several Germans involved in plotting to overthrow Adolf Hitler. This included Dietrich Bonhoeffer, Klaus Bonhoeffer, Josef Mueller and Hans Dohnanyi. Others under suspicion like Wilhelm Canaris and Hans Oster were dismissed from office in January, 1944.
Major Claus von Stauffenberg now emerged as the leader of the group opposed to Nazi rule. In 1942, he decided to kill Adolf Hitler. He was joined by Wilhelm Canaris,Carl Goerdeler, Julius Leber, Ulrich Hassell, Hans Oster, Peter von Wartenburg, Henning von Tresckow, Friedrich Olbricht, Werner von Haeften, Fabian Schlabrendorft, Ludwig Beck and Erwin von Witzleben.
The plot was developed as a modification of Operation Valkyrie (Unternehmen Walküre), which was approved by Hitler for use if Allied bombing of German cities or an uprising of forced laborers from occupied countries working in German factories resulted in a breakdown in law and order. Members of the Reserve Army, including members of the Kreisau Circle, modified the plan and decided to assassinate Adolf Hitler, Hermann Goering and Heinrich Himmler. Afterward, they planned for troops in Berlin to seize key government buildings, telephone and signal centers and radio stations. Hitler's death was required to free German soldiers from their oath of loyalty to him. Operation Valkyrie was meant to give the plotters control over the government so they could make peace with the Allies and end the war.
At least six attempts were aborted before Claus von Stauffenberg decided on trying again during a conference attended by Hitler on July 20, 1944. It was decided to drop plans to kill Goering and Himmler at the same time. Stauffenberg, who had never met Hitler before, carried the bomb in a briefcase and placed it on the floor while he left to make a phone-call. The bomb exploded killing four men in the hut. Hitler's right arm was badly injured but he survived the bomb blast.
The plan was for Ludwig Beck, Erwin von Witzleben and Friedrich Fromm to take control of the German Army. The coup failed in part because they delayed implementing the plan until official confirmation of Hitler's death could be received. When they learned that Hitler had survived, Valkyrie was not put in effect.
In an attempt to protect himself, Fromm organized the execution of Claus von Stauffenberg along with two other conspirators, Friedrich Olbricht and Werner von Haeften, in the courtyard of the War Ministry. It was later reported the Stauffenberg died shouting "Long live holy Germany".
As a result of the July Plot, the new chief of staff, Heinz Guderian demanded the resignation of any officer who did not fully support the ideals of the Nazi Party. Over the next few months Guderian sat with Gerd von Rundstedt and Wilhelm Keitel on the Army Court of Honor that expelled hundreds of officers suspected of being opposed to the policies of Adolf Hitler. This removed them from court martial jurisdiction and turned them over to Roland Freisler and his People's Court.
Over the next few months most of the group, including Wilhelm Canaris, Carl Goerdeler, Julius Leber, Ulrich Hassell, Hans Oster, Peter von Wartenburg, Henning von Tresckow, Ludwig Beck, Erwin von Witzleben and Friedrich Fromm, were either executed or committed suicide. Ninety of the supposed conspirators were executied between August 1944 and April 1945 at the Plotzensee Prison.
It is etimated that 4,980 Germans were executed after the July Plot. Hitler decided that the leaders should have a slow death. They were hung with piano wire from meat-hooks. Their executions were filmed and later shown to senior members of both the NSDAP and the armed forces.
In March 2013, the last surviving member of the plot - Ewald-Heinrich von Kleist-Schmenzin - died in Munich.