Stauffenberg's part in the original plan required him to stay at the Bendlerstraße offices in Berlin, so he could phone regular army units all over Europe in an attempt to convince them to arrest leaders of Nazi political organisations such as the (SD) and the Gestapo. Unfortunately, when General Helmuth Stieff, Chief of Operation at Army High Command, who had regular access to Hitler, backtracked from his earlier commitment to assassinate Hitler, Stauffenberg was forced to take on two critical roles: kill Hitler far from Berlin trigger the military machine in Berlin during office hours of the very same day. Beside Stieff, he was the only conspirator who had regular access to Hitler (during his briefings) by mid-1944, as well as being the only officer among the conspirators thought to have the resolve and persuasiveness to convince German military leaders to throw in with the coup once Hitler was dead. This requirement greatly reduced the chance of a successful coup.