The UB-78 was a type UB III coastal torpedo attack boat built by Blohm and Voss, Hamburg for the Kaiserliche Marine (German Imperial Navy), during the First World War. Ordered on 23rd September 1916 as part of batch UB 75-79, the boat was laid down as hull number 307 and launched on 2nd June, 1917

SM UB-78 Boat Sheet


UB-78 was commissioned in Hamburg on 20th October 1917 to Kapitanleutnant Woldemar Petri. From 2nd January 1918 until 15th February the boat was assigned to V Flottille based out of Bremerhaven. There it undertook one unsuccessful war patrol in the northern North Sea under Petri. Oberleutnant zur See Ulrich Pilzecker then replaced Petri and sailed UB-78 to Bruges, where the boat became part of Flandern I Flottille. Pilzecker then took the boat on an unsuccessful patrol off the east coast of England in late February, returning on 2nd March. He was then assigned to another newly commissioned U-Boat, being replaced by Oberleutnant zur See Alexis Robert Arthur Stoßberg.

SM UB-78 Deck Gun
From the Flanders bases, UB-78 was only able to carry out three patrols, sinking two ships and damaging one. The year 1918 proved to be a difficult year for the U-Boats, mostly because they had to contend with the convoys and their numerous escorts. After UB-78 had torpedoed the collier SS Polleon in the estuary to the Tyne on 22nd March 1918, she was bombarded with 25 depth charges.

She suffered damage to the superstructure where a section of the coning tower had been dented and the jumping wires were damaged. A torpedo had to be wasted on the 86 ton  drifter HMD Border Lads on 28th March 1918 due to the lack of single sailing targets and also because of large presence of enemy on the surface. She damaged two other vessels that month, the Strathearn on 21st March and British Star on 26th March.


UB-78 left Zeebrugge on her final voyage on 18th April 1918, under the command of Stoßberg. However, there is a mystery here. It is recorded that she was laying on the surface trying to detect troop transports, when lookouts on HMS P-33 spotted the surfaced U-Boat. HMS P-33 set a course to ram the U-Boat, but calculated they would eventually collide with the escorted troop ship, the SS Queen Alexandra. HMS P-33 slowed down to enable SS Queen Alexandra to increase speed and go on a ramming course for the U-Boat. Captain Angus Smith increased the speed of his ship to 20 knots and was able to hit UB-78 in her stern compartment, just behind the coning tower and sank at once. HMS P-33 arrived on the spot and dropped a depth charge, but UB-78 had already sunk. The escort marked the location with a buoy at 51° 01″ N 01° 17″ E and accompanied the damaged troop ship back to harbour. The next day, HMS P-33 went back to the location of the sinking to find a 7 mile long track of battery acid and oil on the surface. The date of her sinking is recorded as 19th April 1918.

SM UB-78 is located at 51°1.039 N 01°16.500" E

That said, there is supposition that this victim of SS Queen Alexandra may have been a different U-Boat all together. But which one? Suggestions are U-37, UB-36, UB-113, UB-108, UC-16 or UC-18. Other research suggests the U-Boat rammed by the Alexandra was the UC-78, but that too has it’s conflicting reports as UC-78’s loss could indeed by UC-79, UB-78 being one of the three unidentified UC-II class U-Boats lost to the minefield between the Varne and Fairy Bank.

Questionable Loss

This loss account was called into question by the recovery of the propellers from the wreck. These were stamped UB-78 and “B&V” for Blohm and Voss. With the identity of the wreck as UB-78 proven, the circumstances of loss were investigated by Innes McCartney. He pointed out that the bow of the wreck is pointing south-west, suggesting that the UB-78 was outbound, rather than returning damaged. Furthermore, British naval records indicate that the detonation of a mine was detected in the vicinity of the wreck at 00:30 on 19th April, which is consistent with when Stoßberg’s departure suggests he would have been attempting to breach the Barrage. Furthermore, the missing stern of the wreck reported by divers is only likely to have occurred as a result of a large explosion or impact, such as a mine. It therefore seems overwhelmingly likely that the UB-78 was sunk by a mine whilst trying to penetrate the Dover Barrage outbound on the night of 19-20th April 1918.

Lives Lost

McCartney has suggested that the aft and conning tower hatches of UB-78 were opened by the blast. Whilst this is not certain, it is the case that there were no survivors from the thirty-five onboard.

Oberleutnant zur See Alexis Robert Arthur Stoßberg

Oberleutnant zur See Alexis Robert Arthur Stoßberg

Alexis Robert Arthur Stoßberg was born 7th February 1891 in Kreuznach, Rhineland-Palatinate. Eldest son of Rudolf Stoßberg and Flora Stoßberg (nee Espenscheid). His eldest sister was Irmgard and younger son, Friedrich Otto Hellmut. Source Family Search. He was promoted to Oberleutnant zur See on 2nd May 1915 and was decorated with the Iron Cross 2nd Class, date unknown. He is remembered at the U-Boot-Ehrenmal Möltenort

Protected Place

SM UB-78 is designated as a Protected Place under the Protection of Military Remains Act 1986. The Act makes it an offence to interfere with a protected place, to disturb the site or to remove anything from the site. Divers may visit the site, but the rule is look, don’t touch and don’t penetrate.