In , he was commanding UB , and was taken prisoner of war by British forces. As commander of UB , he attacked a convoy in the Mediterranean while on patrol near Malta.
From to the U-boats fought effectively but lost the initiative from May Furthermore, of these, were lost on their first patrol. Following the war, he was indicted as a major war criminal at the Nuremberg trials on three counts: conspiracy to commit crimes against peace , war crimes , and crimes against humanity ; planning, initiating, and waging wars of aggression ; and crimes against the laws of war. He was found not guilty of committing crimes against humanity, but guilty of committing crimes against peace and war crimes against the laws of war.
He was sentenced to ten years' imprisonment; following his release, he lived in a village near Hamburg until his death in Karl had an older brother. He requested a transfer to the submarine forces, which became effective on 1 October On 2 July , he became commander of UB , operating in the Mediterranean.
He was captured by the British and incarcerated in the Redmires camp near Sheffield. He remained a prisoner of war until and in he returned to Germany. They had three children whom they raised as Protestant Christians: daughter Ursula β and sons Klaus β and Peter β However, on 13 May , his 24th birthday, he persuaded his friends to let him go on the E-boat S for a raid on Selsey. The boat was sunk by the French destroyer La Combattante and Claus was killed. He continued his naval career in the naval arm of the Weimar Republic 's armed forces.
In , the Reichsmarine was renamed Kriegsmarine. Germany was prohibited by the Treaty of Versailles from possessing a submarine fleet. The Anglo-German Naval Agreement of allowed submarines and he was placed in command of the U-boat flotilla Weddigen , which comprised three boats; U-7 ; U-8 and; U He remarked, "Britain, in the circumstances, could not possibly be included in the number of potential enemies.
