including Prussian Finance Minister Johannes Popitz, Planck, and Reichsbank president Hjalmar Schacht approached General Georg Thomas, head of the Defence Economy and Armament Office asking him to thwart the outbreak of the forthcoming Invasion of Poland. Thomas agreed to write a memorandum to his superior, OKW Chief Wilhelm Keitel, in which he stated that a war against Poland would set off a world war that Germany could not win owing to massive supply problems. However, Keitel tried to allay Thomas's fears by telling him that Hitler was planning no such war. In 1940, Planck, Popitz, Ulrich von Hassell and General Ludwig Beck drafted a "Provisional Constitution" on the assumption that the forthcoming attack on the Western Front would overthrow Hitler's regime. Even afterwards, Planck stayed in the conservative resistance circles around Carl Friedrich Goerdeler and was involved in the preparations for the 20 July plot. This led to his arrest on 23 July 1944, after which he was taken to the Gestapo headquarters at the Reichssicherheitshauptamt (RSHA). Erwin Planck was sentenced to death in a show trial at the "People's Court" (Volksgerichtshof) on 23 October. On 25 October, Max Planck personally drafted a letter to Adolf Hitler pleading for Erwin's life, a plea that was ignored. Planck was executed by hanging on 23 January 1945 at Plötzensee Prison in Berlin. Memorial plaque A memorial plaque dedicated to Erwin Planck and his fellow students Paul von Hase and Ernst von Harnack can be found at his old school, the Joachimsthalsches Gymnasium in the Berlin borough of Wilmersdorf. Sources Plötzensee Prison Notes External links Text on the memorial plaque 1893 births 1945 deaths Executed members of the 20 July plot People from Berlin executed at Plötzensee Prison People executed by hanging at Plötzensee Prison Politicians from Berlin People from the Province of Brandenburg Max Planck German prisoners of war in World War I Joachimsthalsches Gymnasium alumni People from Charlottenburg German Army personnel of World War I