Johannmeyer was among the occupants of the "Führerbunker", Hitler's underground headquarters in encircled Berlin. Johannmeyer was present at Hitler's last birthday ceremony on 20 April 1945. During the night of the 28–29 April, Hitler ordered three copies of his political testament be hand-delivered to Field Marshal Ferdinand Schörner in Czechoslovakia, Karl Dönitz in Schleswig-Holstein, and Paul Giesler in Tegernsee by Johannmeyer, SS-"Standartenführer" Wilhelm Zander - Bormann's adjutant, and Chief Press Secretary Heinz Lorenz, respectively. The three officers said their farewell to Hitler and were each handed a white dossier containing the testament by Martin Bormann at approximately 4:00 am on 29 April. Armed with automatic weapons, and in uniform, the trio left Berlin later that day attempting to break through Soviet lines to deliver the testament to their respective objective.