Sea-based fighting during World War II
Submarine warfare in the Black Sea in World War II during 1941 primarily involved engagements between submarines of the Soviet Black Sea Fleet attacking Axis merchantmen defended by Romanian and Bulgarian warships. These engagements were a part of the naval Black Sea campaigns between Axis and Soviet naval forces.
Background.
At the beginning of the war the Soviet Navy enjoyed absolute superiority in terms of submarine warfare, possessing 47 active Submarines in the Black Sea against a single submarine operated by the Romanian Navy, the lonely Delfinul.
Engagements.
On 9 July, the Romanian gunboat "Stihi Eugen" informed the Romanian torpedo boat "Năluca" and motor torpedo boats "Viscolul" and "Vijelia" that the periscope of an enemy submarine was sighted near Mangalia. In the ensuing battle, the Soviet Shchuka-class submarine "Shch-206" was attacked by "Năluca", at first with 20 mm rounds and then with depth charges, eventually being sunk with all hands aboard. According to Romanian sources, a second submarine was also sunk by the two motor torpedo boats.
On 11 August, the Romanian submarine NMS Delfinul was unsuccessfully attacked by M-class submarine "M-33" near Constanța.
On 15 August, the Romanian merchant "Peles" was torpedoed and sunk by the Soviet submarine "ShCh-211" north east of Cape Emine, in Bulgarian waters, while the Italian tanker "Superga" was missed during the same attack.
On 16 August, the Soviet submarine "ShCh-211" attacked once more close Cape Ermine, but missed Romanian merchant "Ardeal".
On 14 September, the Bulgarian merchant "Chipka" sunk after running on a mine laid by Soviet submarine L-4, close Varna.
On 19 September, the Bulgarian auxiliary minesweeper W-2 sunk close Cape Galata due to a mine laid by Soviet submarine L-4 or L-5.
On 5 October, the Romanian destroyer "Regina Maria" was unsuccessfully attacked by Soviet submarine L-4 near Mangalia.
On 10 October, the Romanian auxiliary minelayer NMS Regele Carol I sunk close Cape Galata after running on a mine laid by Soviet submarine L-4 or L-5.
Between 17 and 21 October, the exact date being unclear, the Soviet submarine M-58 was lost; most likely having hit a mine in the Danube estuary area.
On 26 October, the Soviet small submarine M-35 attacked, on surface, a convoy of German barges with gunfire: SF-25 was sunk and SF-36 was heavily damaged and driven ashore off Sulina.
On 3 November, the Turkish sailing vessel Kaynakdere was sunk with gunfire by Soviet submarine Shch-214 close Cape Igneada. After this day, the Soviet submarine M-34 was lost on unclear date near Costanza.
On 5 November, the Italian tanker "Torcello" was torpedoed and sunk by Soviet submarine Shch-214 close Cape Igneada. On the same day, Romanian submarine Delfinul claimed the torpedoing and sinking of the Soviet tanker "Uralles" (1975 GRT) off Yalta, the only known successful torpedo attack from a Romanian submarine during the war. However the tanker was possibly sunk by the Luftwaffe on 29 October while other sources report it was probably attacked by the minelayer Ostrovsky
On 6 November, the Romanian destroyer "Mărășești" was unsuccessfully attacked by the Soviet S-class submarine "S-33" near Mangalia.
Between 12 and 13 November it was likely sunk Soviet submarine S-34 on mines off Bulgarian coast.
After 14 November, the Soviet submarine ShCh-211 was lost in the Romanian defensive mine field "S-18" south of Varna.
On 18 November, the Turkish merchant "Yenice" was torpedoed and sunk in Bulgarian waters by Soviet submarine ShCh-215.
On 29 November, the Soviet submarine "ShCh-211" torpedoed and sunk the Italian tanker "Superga" close Cape Ermine.
On 6 December, the Soviet submarine "Shch-204" was spotted by Bulgarian Arado Ar 196 reconnaissance aircraft near Varna. The Bulgarian submarine chasers "Belomorets" and "Chernomorets", together with the aircraft, attacked and sunk the submarine with depth charges. 
On 17 December, near Jibrieni, the Soviet submarine "M-59" attacked an Axis convoy consisting of the Hungarian cargo ships "Kassa" and "Kolozsvár" and the Bulgarian cargo ship "Tzar Ferdinand", escorted by the Romanian Navy with the Regele Ferdinand-class destroyers "Regele Ferdinand" and "Regina Maria", gunboats "Stihi Eugen" and "Sublocotenent Ghiculescu", and torpedo boats "Sborul" and "Smeul". The attack failed, with "M-59" being depth-charged by "Regele Ferdinand" and sunk with all hands aboard. According other sources, M-59 was lost running on mines earlier in November.
Outcome.
Soviet submarines are estimated to have sunk 10 targets (19,000 tons) of Axis shipping. Gunnery was favoured but many torpedoes were launched, even against shallow-draught targets who were often not hit.
References.
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