Walther Schwieger

Kapitänleutnant Walther Schwieger was a German naval officer and commander of the U-20. On 7 May 1915, he ordered the torpedoing of the RMS Lusitania.

In an alternate timeline, Schwieger did not sink the Lusitania as his ship was hijacked by his prisoner, the Fifth Doctor, so that he would bring him back to the location of his TARDIS. (AUDIO: The Sirens of Time)