Berthold's apartment at Tristanstraße in Berlin, where his brother Claus also lived for some time, was a meeting place for the 20 July conspirators, including their cousin Peter Yorck von Wartenburg. As Claus had access to the inner circle around Hitler, he was assigned to plant a bomb at the "Führer"s briefing hut at the military high command in Rastenburg, East Prussia, on 20 July 1944. Claus then flew to Rangsdorf airfield south of Berlin where he met with Berthold. They went together to "Bendlerstraße", which the coup leaders intended to use as the centre of their operations in Berlin.