At the end of September 1941, Tresckow sent his special operations officer Schlabrendorff to Berlin to contact opposition groups and declare that the staff of Army Group Centre was "prepared to do anything." This approach, made at the height of German expansion and the nadir of anti-Hitler opposition, represented the first initiative to come from the front and from the Army, as Ulrich von Hassell noted in his diary. Schlabrendorff continued to serve as liaison between Army Group Centre and opposition circle around General Ludwig Beck, Carl Friedrich Goerdeler and Colonel Hans Oster, the deputy head of Abwehr (German military intelligence) who was involved in a 1938 coup attempt against Hitler (Oster Conspiracy). Oster's recruitment of General Friedrich Olbricht, head of the General Army Office headquarters, in 1942 linked this asset to Tresckow's resistance group in Army Group Centre, creating a viable coup apparatus.