Colonel Claus Schenk Graf von Stauffenberg, who met Tresckow in August 1943 and worked together on revising Operation Valkyrie, took the responsibility for planning and implementing Hitler's assassination. By the time Stauffenberg was appointed Chief of Staff of the Reserve Army and was ready to carry out the assassination attempt, the Allies had already landed in Normandy. When Stauffenberg sent a message to Tresckow through Lehndorff to ask whether there was any point in making the attempt since there was no practical purpose to be served, Tresckow urged him not only to attempt the assassination but to go ahead with the coup in Berlin even if the assassination were to fail. He argued that there must be an overt act of German opposition to Hitler regardless of the consequences. He also told Philipp von Boeselager and Margarete von Oven that 16,000 people were being killed daily not as casualties of war but from being murdered by the Germans, and Hitler had to be killed just to put an end to it. A few days before the coup attempt, Tresckow confided to a friend that "in all likelihood everything will go wrong". When asked whether the action was necessary nonetheless, he replied, "Yes, even so."