Operation Spark (sometimes translated as "Operation Flash") was the code name for the planned assassination of Nazi dictator Adolf Hitler by the anti-Nazi conspiracy of German Army officers and political conservatives, known as the Schwarze Kapelle ("black orchestra") during World War II. The name was coined by Major General Henning von Tresckow in 1941. He believed that because of Hitler's many successes up to that time, his personal charisma, and the oath of personal loyalty to him sworn by all German army officers, it would be impossible to overthrow Hitler and the Nazis with Hitler still alive. Hitler's death, however, would be a "spark"—a signal that it was time to launch an internal coup d'état to overthrow the Nazi regime and end the war. By early 1943, the failure to overcome the Soviet Union, including the disastrous defeat at Stalingrad, defeats in North Africa, and increasing Allied bombing of Germany had substantially weakened many Germans' allegiance to the Nazi regime. The conspirators decided it was time for the "spark". General Friedrich Olbricht, who controlled the Ersatzheer (Replacement Army) set up a plan for Replacement Army troops to seize control of Germany after Hitler was killed. Tresckow was now serving as Chief Operations Officer of Army Group Centre (AGC) on the Eastern Front. AGC commander Günther von Kluge knew of Tresckow's activities, but did not denounce him to the Gestapo, nor participate himself. He allowed Tresckow to put several other anti-Nazi officers on the AGC staff, but he also tried to dissuade Tresckow from taking action. Major collaborators Major General Henning von Tresckow, Chief Operations Officer of AGC Lieutenant Fabian von Schlabrendorff, Tresckow's Special Operations Officer at AGC Colonel Rudolph-Christoph von Gersdorff, Tresckow's Abwehr Intelligence Liaison Officer Major Georg von Boeselager, commander of cavalry forces near AGC headquarters Captain Axel Freiherr von dem Bussche-Streithorst Captain Eberhard von Breitenbuch Lieutenant Colonel Werner Schrader General Friedrich Olbricht, Chief of the Armed Forces Replacement Office (Wehrersatzamt) Attempts at Army Group Centre Hitler flew to Werwolf, his "field headquarters" near Vinnitsa in Ukraine, on 19 February 1943, staying until 13 March. He decided that before returning to Germany, he would also visit AGC headquarters near Smolensk that same day. He would meet with Kluge, and dine in the officers' mess before departing. This was the first opportunity for his assassination by Tresckow's group. For such an occasion, Tresckow had prepared three options: Major von Boeselager