According to more than one source (including William Shirer in The Rise and Fall of the Third Reich), Field Marshal Erwin Johannes Rommel (1891-1944) became a part of a group of conspirators known as the Schwarze Kapelle (Black Orchestra), and
... Rommel agreed to lend his support to the conspiracy in order to, as he put it, "come to the rescue of Germany."
Rommel, however, did not agree to any plans to assassinate Hitler; instead, he believed that Hitler should be arrested and tried for war crimes. He believed any attempts to kill Hitler would bring the nation to civil war and make Hitler a martyr. He apparently did not join the group until February 1944 when he was recruited by
... three of Rommel's closest friends—Karl Strölin, Alexander von Falkenhausen and Carl Heinrich von Stülpnagel...
They believed it necessary to have an active field marshal as a participant, and Rommel--"The Desert Fox"--was Germany's most famous commander. Rommel was not happy with the failed assassination attempt--or its results--on July 20, 1944, but he became convinced that by that time, Hitler had "gone completely mad." Rommel's participation was revealed by several of the conspirators--one under extreme Gestapo torture. Hitler refused to have the popular Rommel branded a traitor, so he was given the choice of suicide or secret "kangaroo court." Had he been convicted, he and his entire family would probably have been executed; if he was willing to commit suicide, he would receive a hero's burial and his family would receive a full pension. Rommel, ever the heroic figure, chose the cyanide capsule presented him by Hitler's emmisaries.