Thanks to his moral integrity Otto Hahn was trusted everywhere. He used it to point uncompromisingly to three important goals. For him the cessation of nuclear weapon tests, not transferring atomic weapons in order not to let the number of atomic powers become larger, and general disarmament were the essential challenges. Hahn occasionally emphasised that he was not a politician. Yet his speeches, appeals, warnings, and his appearance in public betrayed a purposeful political engagement. His distinctively humanitarian convictions directed him logically to this path.