 Complete the following phrase:  As RSD chief, Rattenhuber was responsible for securing Hitlers field headquarters. Hitlers most famous military FHQ during the war was the Wolfs Lair Wolfsschanze. He spent more time at that Eastern Front military field headquarters than any other. Hitler first arrived at the headquarters in June 1941. In total, he spent more than 800 days there during a three-and-a-half year period until his final departure on 20 November 1944. It was guarded by personnel from the RSD, and Führerbegleitbrigade FBB. The FBK men were also present when Hitler was there. It had several security zones. Sperrkreis 1 Security Zone 1 was located at the heart of the Wolfs Lair. Ringed by steel fencing and guarded by RSD and FBK men, it contained Hitlers bunker and ten other camouflaged bunkers built from thick steel-reinforced concrete. Sperrkreis 2 Security Zone 2 surrounded the inner zone. This area housed the quarters of several Reich ministers, the HQ personnel, two messes, a communication centre, as well as the military barracks for the FBB. Sperrkreis 3 Security Zone 3 was a heavily fortified outer security area which surrounded the two inner zones. It was defended by land mines and FBB personnel, who manned guard houses, watchtowers and checkpoints. Despite the security, the most notable assassination attempt against Hitler was made at the Wolfs Lair on 