Question: Fregattenkapitän Heinrich Lehmann-Willenbrock was a submarine commander in Germany during World War II and the subject of the mini-series called "Das Boot" when he was portrayed by which actor? 
Context: Maurice Herbert Rindskopf (1917–2011) was the youngest officer to ascend to command of a Fleet Submarine in World War II; and until his death, was the last living World War II submarine commander.  His entire World War II submarine career was spent on board  , where he was awarded a Silver Star as a Lieutenant in charge of torpedoes and gunnery, and the Navy Cross as its commanding officer.  He culminated his career as a Rear Admiral and the Director of Naval Intelligence. Fregattenkapitän Heinrich Lehmann-Willenbrock (11 December 1911 – 18 April 1986) was a submarine commander in the "Kriegsmarine" of Nazi Germany during World War II.  He was sixth among the top ten successful U-boat commanders during the Battle of the Atlantic against the Allies, in terms of tonnage of merchant ships sunk.  He commanded four U-boats, and his most successful tour was commanding the "U-96" a Type VIIC U-boat, which gained widespread recognition when one of its patrols was documented and publicized by an accompanying member of a propaganda company Lothar-Günther Buchheim.  He was awarded the Knight's Cross of the Iron Cross with Oak Leaves.  The story of the "U-96" was eventually made into a mini-series and film called "Das Boot", in which he was portrayed by Jürgen Prochnow. Hans Heinrich Hass (12 October 1922 - 21 January 2009), aka "Hans-Heinrich Haß", was a German submarine commander who served in both the Kriegsmarine of Nazi Germany and later in the post war Bundesmarine of West Germany.  As a junior Midshipman, he served on board the German submarine "U-96" during its famous 7th war patrol under the command of Heinrich Lehmann-Willenbrock.  Hass was later the basis for one of the characters in the novel "Das Boot" by author Lothar-Günther Buchheim. Commander James Stuart "Jimmy" Launders, (1919–1988) was an officer in the Royal Navy during and after World War II.  He retired from the service in 1974, but continued to serve in an unofficial capacity on training programs until his death in 1988.  In addition to his reputation amongst his crew, colleagues, and historians as a brilliant, highly skilled, and courageous commander, Launders is remembered as the only submarine commander in history to have engaged and sunk an enemy submarine ("U-864") during time of war using only his own unaided vessel (HMS "Venturer" ) while both ships were fully submerged.  The unique type of engagement and the unusual nature of the enemy submarine's mission has provided one of the more enduring footnotes to the war, further cementing the fame of Launders, "Venturer", and her crew for their wartime action. Dudley Walker "Mush" Morton (July 17, 1907 – October 11, 1943) was a submarine commander of the United States Navy during World War II.  He was commander of  during its third through seventh patrols.  "Wahoo" was one of the most-celebrated submarines of World War II, sinking at least 19 Japanese ships, more than any other submarine of the time.  Morton and "Wahoo" disappeared in 1943 during a patrol near La Perouse Strait, and he was ultimately declared deceased three years later. Martin Semmelrogge (born 8 December 1955 in Boll-Eckwälden, Bad Boll, West Germany) is a German actor, best known for his role as the comical Second Watch Officer in the film "Das Boot".  His character was based on the real life World War II submarine officer Werner Herrmann. Das Boot (] , German meaning "The Boat") is a 1981 German war film written and directed by Wolfgang Petersen, produced by Günter Rohrbach, and starring Jürgen Prochnow, Herbert Grönemeyer, and Klaus Wennemann.  It has been exhibited both as a theatrical release and as a TV miniseries (1985), in several different home video versions of various running times, and in a longer director's cut version supervised by Petersen in 1997. Werner Herrmann (born 1920) was a German submarine commander during World War II who was the basis for the character of the "Second Watch Officer" in both the novel and film "Das Boot".  In the film version, he is portrayed by actor Martin Semmelrogge. Hans Peter Dengel (28 Nov 1916 - 2 July 1944) was an engineering officer of the Kriegsmarine during World War II who served as chief engineer of the famous U-boat U-96 during its later war patrols under the command of Heinrich Lehmann-Willenbrock.  Dengel was killed on-board U-543 when that boat was struck by fire from Allied aircraft.  He was the inspiration for the character of "the Chief" in both the novel and film "Das Boot".  In the film, he was portrayed by German actor Klaus Wennemann. German submarine "U-96" was a Type VIIC U-boat of Nazi Germany's "Kriegsmarine" during World War II.  Her keel was laid down on 16 September 1939, by Germaniawerft, of Kiel as yard number 601.  She was commissioned on 14 September 1940, with "Kapitänleutnant" Heinrich Lehmann-Willenbrock in command.  Lehmann-Willenbrock was relieved in March 1942 by "Oberleutnant zur See" Hans-Jürgen Hellriegel, who was relieved in turn in March 1943 by "Oblt.z.S."  Wilhelm Peters.  In February 1944, "Oblt.z.S."  Horst Willner took command, turning the boat over to "Oblt.z.S."  Robert Rix in June of that year.  Rix commanded the boat until February 1945.  During 1941, war correspondent Lothar-Günther Buchheim joined "U-96" for a single patrol.
Answer: Jürgen Prochnow