<sod>On 14 October 1939, Prien risked shallow water, unknown shoals, tricky currents and detection by defenders to penetrate the [[Royal Navy]]'s primary base, [[Scapa Flow]]. Although most of the [[Home Fleet]] was at sea, Prien sank the battleship {{HMS|Royal Oak|08|2}} and returned home to instant fame. He was awarded the [[Knight's Cross of the Iron Cross]], personally by [[Adolf Hitler]], and was the first sailor of the U-boat service and the second member of the ''[[Kriegsmarine]]'' to receive this award. The mission into Scapa Flow called for volunteers only; Prien had no hesitation in accepting the mission. In a token to the voluntary nature of the mission, Prien spoke to his crew while ''U-47'' was lying off Scapa Flow, and having briefed them, he announced that anyone not wishing to volunteer could leave the boat immediately. Unsurprisingly, no one accepted the offer to disembark in the middle of the North Sea. Prien received the nickname ''Der Stier von Scapa Flow'' (''"The Bull of Scapa Flow"''); the emblem of a snorting bull was painted on the conning tower of ''U-47'' and soon became the emblem of the entire [[7th U-boat Flotilla]]. Two members of the Scapa Flow crew earned the Knight's Cross of the Iron Cross during World War II: the chief engineer (''[[Leitender Ingenieur]]'') [[Johann-Friedrich Wessels]] and 1st watch officer (''I. Wachoffizier'') [[Engelbert Endrass]].<eod>
<sod>On 14 October 1939, Prien's boat penetrated the [[Royal Navy]]'s primary base, [[Scapa Flow]] and sank the battleship {{HMS|Royal Oak|08|2}}. He returned to Germany to instant fame. He was awarded the [[Knight's Cross of the Iron Cross]], personally by [[Adolf Hitler]], the first sailor of the U-boat service and the second member of the ''[[Kriegsmarine]]'' to receive this award. Prien received the nickname ''Der Stier von Scapa Flow'' (''"The Bull of Scapa Flow"''); the emblem of a snorting bull was painted on the conning tower of ''U-47'' and soon became the emblem of the entire [[7th U-boat Flotilla]]. Two members of the Scapa Flow crew earned the Knight's Cross of the Iron Cross during World War II: the chief engineer (''[[Leitender Ingenieur]]'') [[Johann-Friedrich Wessels]] and 1st watch officer (''I. Wachoffizier'') [[Engelbert Endrass]].<eod>