Wartime Photograph (Postcardsize) and Visitor Card of Günther Seibicke. Seibicke (30 August 1911 – 26 May 1943) was a German U-boat commander in World War II and recipient of the Knight’s Cross of the Iron Cross (Ritterkreuz des Eisernen Kreuzes). The Knight’s Cross of the Iron Cross was awarded to recognise extreme battlefield bravery or successful military leadership. He and the entire crew of U-436 were killed on 26 May 1943 by depth charges from the British frigate HMS Test and the corvette HMS Hyderabad.