Twenty-two-year-old Oberleutnant zur See Eberhard Dahlhaus had an unusually intense patrol of nineteen days in the southeast corner of the region covered. To get to the Caribbean U-634 crossed Biscay with U-159, U-185, U-415 and U-564. As covered, U-564 was damaged by a Sunderland bomber. The boat succumbed to this attack and her crew were rescued by U-185, which turned back to base. The remaining boats steamed west and were refueled by U-488 west of the Azores. During this patrol the submarine met with no Allied ships (Wynn, Vol. 2, p.97).
Normally submarines which transit the Anegada Passage enter and exit the region in a matter of hours, however Dahlhaus chose to remain northeast of Puerto Rico for over two weeks. He originally entered inbound on the 13th of July 1943 and then patrolled north of San Juan for over a week, between the 15thand the 26th. After that, by the 27th of July, the boat entered the Mona Passage and thus exited the region. This patrol was by necessity reconstructed from radio reports, as the boat was sunk.
On the 7th of August Dahlhaus returned to transit the Anegada Passage, then turned northwest to again patrol to the north of Puerto Rico and the Virgin Islands. On the 9thof August, having found no prey, the submarine steamed north to meet its fate, exiting the area on the 11th of August, about one third of the distance to Bermuda. On the 19th of August U-634 gave some of her extra fuel to U-230 in mid Atlantic so the other sub could extend its patrol.
On the 30th of August U-634 was detected by the British warships HMS Storkand HMS Stonecrop east of the Azores. The Allies were protecting the convoy MKS 22/SL. They dropped patterns of depth-charges, probably utilizing the hedgehog device which launched the bombs forward of the ship, allowing it to retain sonar contact with the target. The boat was sunk and all 48 men on board killed (Wynn, Vol. 2, p.97).
U-634’s previous skipper was Hans-Günther Brosin, however Dahlhaus made more of a name for himself not just for the one ship sunk and 7,176. Not only was Dahlhaus the youngest skipper to patrol the Bahamas area, but he was also the youngest German submarine commander at the time. Born on 24 July 1920 he was 22 years of age. A member of the Crew of 1938, Dahlhaus was an experienced officer who returned to sea for three patrols of 153 days despite the horrific death rate on submarines at the time. Promoted to Oberleutnant zur See on the 1st of March 1943, Dahlhaus earned the Iron Cross First Class before his youthful end.
SOURCES: Gudmundur Helgason, Rainer Kolbicz, www.uboat.net, 2011, Kenneth Wynn, U-boat Operations of the Second World War, Volume 1 and Volume 2, 1997