The role that Rommel played in the military's resistance against Hitler or the 20 July plot is difficult to ascertain, as most of the leaders who were directly involved did not survive and limited documentation on the conspirators' plans and preparations exists. One piece of evidence that points to the possibility that Rommel came to support the assassination plan was General Eberbach's confession to his son (eavesdropped on by British agencies) while in British captivity, which stated that Rommel explicitly said to him that Hitler and his close associates had to be killed because this would be the only way out for Germany. This conversation occurred about a month before Rommel was coerced into committing suicide. Other notable evidence includes the papers of Rudolf Hartmann (who survived the later purge) and Carl-Heinrich von Stülpnagel, who were among the leaders of the military resistance (alongside Rommel's chief of staff General Hans Speidel, Colonel Karl-Richard Koßmann, Colonel Eberhard Finckh and Lieutenant Colonel Caesar von Hofacker). These papers, accidentally discovered by historian Christian Schweizer in 2018 while doing research on Rudolf Hartmann, include Hartmann's eyewitness account of a conversation between Rommel and Stülpnagel in May 1944, as well as photos of the mid-May 1944 meeting between the inner circle of the resistance and Rommel at Koßmann's house. According to Hartmann, by the end of May, in another meeting at Hartmann's quarters in Mareil–Marly, Rommel showed "decisive determination" and clear approval of the inner circle's plan.