Late on the evening of November 10, Groener telephoned Ebert at the Reichskanzlei using a secret line, the existence of which had been unknown to Ebert until that time.
Following the initial telephone call, Ebert and Groener talked each evening over a secret line between the Reichskanzlei in Berlin and the headquarters (first at Spa, then at Kassel) as Groener wrote in his memoirs "about the necessary measures" [REF].