.
| Operator | Ship | Class | Cause | Location |
|---|
| January 3 | | '''S-2''' | '''S''' class submarine | Sunk by Finnish mine | Märket narrows, Baltic Sea |
|---|
| January 7 | | 'HMS ''Seahorse''' | '''S''' class submarine | Deptcharged and sunk by ships of the German 1st Minesweeping Flotilla | North-west of Heligoland |
|---|
| January 7 | | 'HMS ''Undine''' | '''U''' class submarine | Sunk by German A/S trawlers | South west of Heligoland |
|---|
| January 9 | | 'HMS ''Starfish''' | '''S''' class submarine | Deptcharged and sunk by German minesweeper '''M-7''' | Heligoland Bight |
|---|
| January 13 | | '''Aura II''' | Escort vessel and former presidential yacht | Sunk by one of her own depth charges as it exploded in its thrower while she was attacking the Soviet submarine '''ShCh-324''' | Märket narrows, Baltic Sea |
|---|
| January 19 | | 'HMS ''Grenville''' | '''G''' class destroyer | Sunk by mine | North Sea |
|---|
| January 21 | | 'HMS ''Exmouth''' | '''E''' class destroyer | Torpedoed and sunk by U-22 | In the Moray Firth, off Inverness |
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| January 30 | | '''Unterseeboot 15''' | Submarine | Collision with torpedo boat '''Iltis''' | North Sea, near Hoofden |
|---|
| January 30 | | '''Unterseeboot 55''' | Submarine | Sunk by RN destroyer 'HMS ''Whitshed''', RN sloop 'HMS ''Fowey''', French destroyers '''Valmy'''. '''Guepard''' and a Short Sunderland from No. 228 Squadron RAF | North Sea near the Shetland Islands |
|---|
| February 5 | | '''Unterseeboot 41''' | Submarine | Sunk by 'HMS ''Antelope''' | South of Ireland |
|---|
| February 12 | | '''Unterseeboot 33''' | Submarine | Sunk by the minesweeper 'HMS ''Gleaner''' | Firth of Clyde |
|---|
| February 18 | | 'HMS ''Daring''' | '''D''' class destroyer | Torpedoed and sunk by ''U-23'' | East of Pentland Firth, Scotland |
|---|
| February 20 | | '''Unterseeboot 54''' | Submarine | Disappeared, probably lost to mine field | North Sea |
|---|
| February 22 | | '''Leberecht Maass''' | '''Zerstörer 1934''' class destroyer | Attacked and hit by a Luftwaffe bomber, lost steering and strayed into a British minefield | Dogger Bank |
|---|
| February 22 | | '''Max Schultz''' | '''Zerstörer 1934''' class destroyer | Hit mine during rescue efforts for '''Leberecht Maass' | Dogger Bank |
|---|
| February 23 | | '''Unterseeboot 53''' | Submarine | Depth charged and sunk by RN destroyer 'HMS ''Gurkha''' | North Sea, near Orkney |
|---|
| February 25 | | '''Unterseeboot 63''' | Submarine | Sunk by the destroyers 'HMS ''Escort''', 'HMS ''Inglefield''', and 'HMS ''Imogen''' | North Sea near the Shetland Islands |
|---|
| March 13 | | '''Unterseeboot 44''' | Submarine | Lost in mine field | North Sea |
|---|
| March 24 | | '''La Railleuse''' | '''L'Adroit''' class destroyer | Sunk by accidental explosion of its own torpedoes | Casablanca, Marocco |
|---|
| March 27 | | '''Unterseeboot 22''' | Submarine | Went missing | North Sea |
|---|
| April 6 | | '''Unterseeboot 1''' | Submarine | Sunk by mine | North Sea |
|---|
| April 6 | | '''Unterseeboot 50''' | Submarine | Sunk by mine | North Sea north of Terschelling |
|---|
| April 8 | | 'HMS ''Glowworm''' | '''G''' class destroyer | Sunk by the German cruiser Admiral Hipper at the beginning of the German invasion of Norway | North-west of Trondheim |
|---|
| April 9 | | 'HMS ''Gurkha''' | '''Tribal''' class destroyer | Sunk by Luftwaffe bombers in the initial phase of Operation Weserübung | North Sea south-east of Bergen |
|---|
| April 9 | | 'HNoMS ''A-2''' | '''A''' class submarine | Attacked and totally wrecked by German Raum-boats 'R-22' and 'R-23' | Off Tønsberg, Oslofjord |
|---|
| April 9 | | 'HNoMS ''Æger''' | '''Sleipner''' class destroyer | Sunk by Luftwaffe bombersduring the invasion of Norway | Near Stavanger |
|---|
| April 9 | | '''Blücher''' | '''Admiral Hipper''' class heavy cruiser | Sunk by Norwegian coastal artillery and shore-based torpedoes during Operation Weserübung | Oslofjord |
|---|
| April 9 | | 'HNoMS ''Eidsvold''' | '''Eidsvold''' class coastal battleship | Torpedoed by the German destroyer ''Wilhelm Heidkamp''during the battle of Narvik | Narvik |
|---|
| April 9 | | 'HNoMS ''Norge''' | '''Eidsvold''' class coastal battleship | Torpedoed by the German destroyer ''Bernd von Arnim''during the battle of Narvik | Narvik |
|---|
| April 9 | | '''Karlsruhe''' | '''K''' class light cruiser | Torpedoed and crippled by British submarine 'HMS ''Truant' off Kristiansand while on her way back to Germany after taking part in Operation Weserübung, then scuttled by German torpedoboat ''Greif'' | Skagerrak near Kristiansand |
|---|
| April 10 | | '''Albatros''' | '''1923 Raubvogel''' class torpedoboat | Accidentally grounded and wrecked during battle with Oslofjord Fortress | Oslofjord |
|---|
| April 10 | | '''Wilhelm Heidkamp''' | '''Zerstörer 1936''' class destroyer | Torpedoed by the British destroyer HMS ''''Hardy'' during first battle of Narvik | Narvik |
|---|
| April 10 | | '''Anton Schmitt''' | '''Zerstörer 1936''' class destroyer | Torpedoed by the British destroyer HMS ''''Hunter'' during first battle of Narvik | Narvik |
|---|
| April 10 | | 'HMS ''Hardy''' | '''H''' class destroyer | Sunk by German destroyers during first battle of Narvik | Ofotfjord near Narvik |
|---|
| April 10 | | 'HMS ''Hunter''' | '''H''' class destroyer | Sunk by German destroyers during first battle of Narvik | Ofotfjord near Narvik |
|---|
| April 10 | | '''Königsberg''' | '''K''' class light cruiser | Bombed and sunk by Fleet Air Arm Blackburn Skua dive bombers while in port in Bergen on the second day of Operation Weserübung | Bergen |
|---|
| April 10 | | 'HMS ''Tarpon''' | '''T''' class submarine | Probably sunk by the German 'Q-ship' '''Schiff 40 / Schürbek''' and the minesweeper '''M6''' | Skagerak |
|---|
| April 10 | | 'HMS ''Thistle''' | '''T''' class submarine | Torpedoed and sunk by U-4 during the Operation Weserübung | North Sea off Norway |
|---|
| April 13 | | 'HNoMS ''Frøya''' | Minelayer | Scuttled by own crew during the Norwegian campaign, then torpedoed and destroyed by U-34 | Trondheimsfjord |
|---|
| April 13 | | '''Unterseeboot 64''' | Submarine | Sunk by Fairey Swordfish from HMS Warspite during the Second Battle of Narvik | Near Bjerkvik |
|---|
| April 13 | | '''Erich Koellner''' | '''Zerstörer 1934A''' class destroyer | Sunk by HMS Warspite and RN destroyers during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Hermann Künne''' | '''Zerstörer 1936''' class destroyer | Sunk by HMS Eskimo during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Diether von Roeder''' | '''Zerstörer 1936''' class destroyer | Sunk by HMS Warspite and RN destroyers during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Erich Giese''' | '''Zerstörer 1934A''' class destroyer | Sunk by HMS Warspite and RN destroyers during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Bernd von Arnim''' | '''Zerstörer 1934A''' class destroyer | Scuttled by own crew during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Georg Thiele''' | '''Zerstörer 1934''' class destroyer | Scuttled by own crew during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Hans Lüdemann''' | '''Zerstörer 1936''' class destroyer | Scuttled by own crew during the Second Battle of Narvik | Narvik |
|---|
| April 13 | | '''Wolfgang Zenker''' | '''Zerstörer 1934A''' class destroyer | Scuttled by own crew during the Second Battle of Narvik | Narvik |
|---|
| April 15 | | '''Brummer''' | Auxiliary gunnery training ship | Torpedoed by RN submarine 'HMS ''Sterlet''' April 14, sinking early the next morning | Kattegat |
|---|
| April 15 | | '''Unterseeboot 49''' | Submarine | Sunk by British destroyers 'HMS ''Fearless''' and 'HMS ''Brazen''' | Near Harstad |
|---|
| April 16 | | 'HNoMS ''A-3''' | '''A''' class submarine | Scuttled by own crew to prevent capture by the Germans | Verkbukta, Tønsberg |
|---|
| April 16 | | 'HNoMS ''A-4''' | '''A''' class submarine | Scuttled by own crew to prevent capture by the Germans | Verkbukta, Tønsberg |
|---|
| April 18 | | 'HMS ''Sterlet''' | '''S''' class submarine | Sunk either by German anti submarine trawlers '''UJ-125''', '''UJ-126''' and '''UJ-128''' or mined on her way home to base | Skagerrak south of Larvik |
|---|
| April 20 | | 'HNoMS ''Stegg''' | '''Trygg''' class torpedo boat | Sunk in battle with Kriegsmarine warships during the Norwegian campaign | Hardangerfjord |
|---|
| April 26 | | 'HNoMS ''Garm''' | '''Draug''' class destroyer | Sunk by Luftwaffe bombers during the Norwegian campaign | Sognefjord |
|---|
| April 29 | | 'HMS ''Unity''' | '''U''' class submarine | Sunk following accidental collision with Norwegian Steamer '''Atle Jarl''' | Off the Tyne |
|---|
| April 30 | | 'HMS ''Bittern''' | '''Bittern''' class sloop | Sunk by German bombers during the Norwegian campaign | Off Namsos |
|---|
| April 30 | | 'HMS ''Dunoon''' | '''Hunt''' class minesweeper | Mined while sweeping for mines | Off Great Yarmouth |
|---|
| April 30 | | '''Leopard''' | '''1924 Raubtier''' class torpedoboat | Sunk after collision with the minelayer '''Preußen''' | Skagerrak |
|---|
| April 30 | | '''Maillé Brézé''' | '''Vauquelin''' class destroyer | Sunk by accidental explosion of two of its own torpedoes | Greenock, Scotland |
|---|
| May 1 | | 'HMS ''Aston Villa''' | ASW trawler | Sunk by Stuka dive bombers during the Namsos campaign | Namsos |
|---|
| May 1 | | 'HMS ''Gaul''' | ASW trawler | Sunk by Stuka dive bombers during the Namsos campaign | Namsos |
|---|
| May 1 | | 'HMS ''St. Goran''' | ASW trawler | Severly damaged by Luftwaffe bombers during the Namsos campaign, then scuttled by HMS ''Angle'' | Namsos |
|---|
| May 1 | | '''Uller''' | '''Vale''' class minelayer | Sunk by Royal Norwegian Navy Air Service Heinkel He 115 seaplane bomber | Sognefjord |
|---|
| May 3 | | '''Bison''' | '''Guépard''' class destroyer | Sunk by German aircraft while taking part in the evacuation of Namsos | Off Trondheim |
|---|
| May 3 | | 'HMS ''Afridi''' | '''Tribal''' class destroyer | Sunk by Stuka dive bombers during the evacuation of troops from the Namsos campaign | Namsos |
|---|
| May 4 | | 'ORP ''Grom''' | '''Grom''' class destroyer | Sunk by German bombers | Ofotfjord near Narvik |
|---|
| May 9 | | '''Doris''' | '''Circé''' class submarine | Torpedoed and sunk by U-9 | West of Petten, the Netherlands |
|---|
| May 10 |  22x20px Royal Netherlands Navy | 'HNLMS ''Van Galen''' | '''Admiralen''' class destroyer | Severely damaged by German bombers off Waalhaven, sinking later in the day | Merwedehaven |
|---|
| May 12 |  22x20px Royal Netherlands Navy | 'HNLMS ''Friso''' | '''Gruno''' class gunboat | Sunk by German aircraft | On the IJsselmeer off Enkhuizen |
|---|
| May 13 |  22x20px Royal Netherlands Navy | 'HNLMS ''Christiaan Cornelis''' | '''K''' class torpedoboat | Scuttled by own crew after suffering heavy damage from German air and ground forces | Rotterdam |
|---|
| May 14 |  22x20px Royal Netherlands Navy | 'HNLMS ''Brinio''' | '''Gruno''' class gunboat | Scuttled by own crew after suffering damage from German aircraft on May 12 | On the IJsselmeer |
|---|
| May 14 |  22x20px Royal Netherlands Navy | '''O 11''' | '''O 9''' class submarine | Scuttled to prevent capture by the Germans | Den Helder |
|---|
| May 14 |  22x20px Royal Netherlands Navy | '''O 12''' | '''O 12 class''' class submarine | Scuttled to prevent capture by the Germans while undergoing maintenance at the 'Rijkswerf' shipyard | Den Helder |
|---|
| May 15 |  22x20px Royal Netherlands Navy | 'HNLMS ''Hydra''' | '''Hydra''' class minelayer | Beached and scuttled by her own crew after being damaged by German anti-tank gunfire | Somewhere in Zeeland |
|---|
| May 15 |  22x20px Royal Netherlands Navy | 'HNLMS ''Tjerk Hiddes''' | '''Gerard Callenburgh''' class destroyer | Scuttled to prevent capture by the Germans | Nieuwe Waterweg at Rotterdam |
|---|
| May 15 | | 'HMS ''Valentine''' | '''V''' class destroyer | Bombed by German aircraft, beached and abandoned | Off Terneuzen, Holland |
|---|
| May 17 |  22x20px Royal Netherlands Navy | 'HNLMS ''Philips Van Almonde''' | '''Gerard Callenburgh''' class destroyer | Scuttled on slipway to prevent capture by the Germans | Vlissingen |
|---|
| May 18 | | 'HMS ''Effingham''' | '''Hawkins''' class cruiser | Wrecked on a reef near Bodø during the Norwegian campaign, scuttled with gunfire and torpedoes by HMS '''Matabele''' 21 May 1940 | Bliksvær near Bodø |
|---|
| May 19 | | 'HMS ''Whitley''' | '''W''' class destroyer | Damaged by German aircraft, beached, then scuttled by 'HMS ''Keith''' | Off Ostend |
|---|
| May 21 | | '''L'Adroit''' | '''L'Adroit''' class destroyer | Sunk by German He 111 bomber | Off Dunkerque |
|---|
| May 23 | | '''Jaguar''' | '''Chacal''' class destroyer | Sunk by E-boats '''S-21''' and '''S-23''' during Operation Dynamo | Off Dunkerque |
|---|
| May 23 | | '''Orage''' | '''Bourrasque''' class destroyer | Sunk by German bombers | Off Boulogne-sur-Mer |
|---|
| May 24 | | '''Chacal''' | '''Chacal''' class destroyer | Sunk by German aircraft | Off Boulogne-sur-Mer |
|---|
| May 24 | | 'HMS ''Wessex''' | '''W''' class destroyer | Bombed and sunk by German aircraft while conducting a NGFS mission | Off Calais |
|---|
| May 26 | | 'HMS ''Curlew''' | '''C''' class light cruiser | Sunk by German bombers | Ofotfjord near Narvik |
|---|
| May 29 | | 'HMS ''Grafton''' | '''G''' class destroyer | Sunk by the German uboat U-62 during Operation Dynamo | North Sea, off Nieuwpoort, Belgium, Belgium |
|---|
| May 29 | | 'HMS ''Grenade''' | G class destroyer | Sunk by Stukas during Operation Dynamo | English Channel |
|---|
| May 29 | | 'HMS ''Wakeful''' | W class destroyer | Torpedoed and sunk by E-boat 'S-30' during Operation Dynamo | English Channel |
|---|
| May 30 | | '''Bourrasque''' | '''Bourrasque''' class destroyer | Heavily damaged by mine, then sunk by artillery fire during Operation Dynamo | North Sea, off Nieuwpoort, Belgium, Belgium |
|---|
| May 31 | | '''Sirocco''' | '''Bourrasque''' class destroyer | Sunk by E-boats '''S-23''' and '''S-26''' during Operation Dynamo | English Channel |
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| May 31 | | '''Unterseeboot 13''' | Submarine | Sunk by Royal Navy sloop HMS ''Weston'' |
|---|
| Late May | | 'ORP ''Orzeł''' | '''Orzeł''' class submarine | Disappeared while operating against German naval forces off Norway during the Norwegian campaign | Somewhere in the North Sea |
|---|
| June 1 | | 'HMS ''Basilisk''' | '''B''' class destroyer | Sunk by air attack during Operation Dynamo | English Channel |
|---|
| June 1 | | 'HMS ''Havant''' | '''Havant''' class destroyer | Damaged by air attack, then sunk by 'HMS ''Saltash''' during Operation Dynamo | English Channel |
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| June 1 | | 'HMS ''Keith''' | '''B''' class destroyer | Sunk by air attack during Operation Dynamo | English Channel |
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| June 1 | | '''Le Foudroyant''' | '''L'Adroit''' class destroyer | Sunk by air attack during Operation Dynamo | English Channel |
|---|
| June 7 | | 'HMS ''Carinthia''' | Armed merchant cruiser | Torpedoed by '''U-46''' on June 6, foundered the next day | West of Galway Bay, Ireland |
|---|
| June 8 | | 'HMS ''Acasta''' | '''A''' class destroyer | Sunk by the German battlecruisers ''Gneisenau'' and ''Scharnhorst'' during Operation Juno | North Sea near Norway |
|---|
| June 8 | | 'HMS ''Ardent''' | '''A''' class destroyer | Sunk by the German battlecruisers ''Gneisenau'' and ''Scharnhorst'' during Operation Juno | North Sea near Norway |
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| June 8 | | 'HMS ''Glorious''' | Aircraft carrier | Sunk by the German battlecruisers ''Gneisenau'' and ''Scharnhorst'' during Operation Juno | North Sea near Norway |
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| June 8 | | 'HMS ''Juniper ''' | '''Tree''' class minesweeping trawler | Sunk by the German heavy cruiser ''Admiral Hipper'' during Operation Juno | North Sea near Norway |
|---|
| June 10 | | 'HNoMS ''B-3''' | '''B''' class submarine | Scuttled by her own crew to prevent capture by the Germans after battery explosion | Alsvåg, Vesterålen |
|---|
| June 12 | | 'HMS ''Calypso''' | '''C''' class light cruiser | Sunk by Italian submarine Bagnolini | Eastern Mediterranean, south of Crete |
|---|
| June 13 |  22x20px Royal Netherlands Navy | '''O 13''' | '''O 12 class''' class submarine | Went missing on patrol, probably lost in German mine field June 13 | Near the Great Fisher Bank |
|---|
| June 13 | | 'HMS ''Scotstoun''' | Armed merchant cruiser | Torpedoed and sunk by '''U-25''' | West of Barra, Outer Hebrides |
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| June 14 | Regia Marina | '''Macalle''' | '''Adua''' class submarine | Ran aground | Red Sea |
|---|
| June 14 | | 'HMS ''Odin''' | '''Odin''' class submarine | Sunk by the Italian destroyers Strale and Baleno | In the Gulf of Taranto, off Crotone |
|---|
| June 16 | | 'HMS ''Grampus''' | '''Grampus''' class submarine | Sunk by four Italian Spica class torpedo boats | East of Sicily |
|---|
| June 17 | | '''HMT Lancastria''' | Troopship | Sunk by air attack during Operation Ariel | South of Chémoulin Point in the Charpentier roads off St. Nazaire |
|---|
| June 17 | Regia Marina | '''Provana''' | '''Marcello''' class submarine | Rammed and sunk by French sloop '''La Curieuse''' after attacking a French convoy | Off Oran, Algeria |
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| June 18 | | '''Achille''' | '''Redoutable''' class submarine | Scuttled while in drydock | Brest |
|---|
| June 18 | | '''Agosta''' | '''Agosta''' class submarine | Scuttled | Brest |
|---|
| June 18 | | '''Cyclone''' | '''Bourrasque''' class destroyer | Damaged by E-boat '''S-24''' 30 May 1940, scuttled June 18 1940 | Brest |
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| June 18 | | '''Pasteur''' | '''Redoutable''' class submarine | Scuttled | Brest |
|---|
| June 18 | | '''Ouessant''' | '''Agosta''' class submarine | Scuttled | Brest |
|---|
| June 19 | | 'HMS ''Orpheus''' | '''Odin''' class submarine | Sunk by the Italian '''Turbine''' class destroyer '''Turbine''' | North of Tobruk |
|---|
| June 20 | Regia Marina | '''Diamante''' | Submarine | Torpedoed and sunk by 'HMS ''Parthian''' | Off Tobruk |
|---|
| June 22 | | '''La Bastiaise''' | '''Flower''' class corvette | Sunk by mine | Off Hartlepool |
|---|
| June 22 | | '''Unterseeboot 122''' | Submarine | Lost to reasons unknown | North Sea |
|---|
| June 23 | Regia Marina | '''Torricelli''' | Submarine | Sunk in surface gunbattle with the destroyers 'HMS ''Kandahar''', 'HMS ''Kingston''', 'HMS ''Khartoum''' and the sloop 'HMS ''Shoreham''' | Red Sea off Perim |
|---|
| June 23 | | 'HMS ''Khartoum''' | '''K''' class destroyer | Beached after suffering heavy gunfire damage in battle with the Italian submarine '''Torricelli''' | Red Sea off Perim |
|---|
| June 23 | Royal Indian Navy | 'HMIS ''Pathan''' | '''PC''' class patrol craft | Torpedoed and sunk by the Italian submarine '''Galvani''' | Gulf of Oman |
|---|
| June 24 | Regia Marina | '''Galvani''' | '''Brin''' class submarine | Engaged on the surface and sunk by the sloop 'HMS ''Falmouth' | Gulf of Oman |
|---|
| June 25 | | 'HMCS ''Fraser''' | '''C''' class destroyer | Accidentally rammed and sunk by anti-aircraft cruiser 'HMS ''Calcutta''' during Operation Ariel | Gironde estuary, off Bordeaux |
|---|
| June 27 | Regia Marina | '''Console Generale Liuzzi''' | '''Liuzzi''' class submarine | Scuttled after depth charge attack from RN destroyers HMS ''Dainty'', 'HMS ''Ilex''', 'HMS ''Decoy''', 'HMS ''Defender''', and RAN destroyer 'HMAS ''Voyager''' | South of Crete |
|---|
| June 28 | Regia Marina | '''Espero''' | '''Turbine''' class destroyer | Sunk by 'HMAS ''Sydney''' while transporting Black Shirts from Taranto to Tobruk | Off Tobruk |
|---|
| June 29 | | 'HMS ''Edgehill''' | Special service vessel (Q-ship) | Torpedoed and sunk by U-51 | In the North Atlantic, south-west of Ireland |
|---|
| June 29 | Regia Marina | '''Argonauta''' | '''Argonauta''' class submarine | Probably sunk by depth charge attack from RN destroyers HMS ''Dainty'', 'HMS ''Ilex''', 'HMS ''Decoy''', 'HMS ''Defender''', and RAN destroyer 'HMAS ''Voyager''', alternatively depth charged and sunk by a Short Sunderland | Off Cape Ras el Hilal, Libya |
|---|
| June 29 | Regia Marina | '''Rubino''' | '''Sirena''' class submarine | Sunk by Short Sunderland of No. 230 Squadron RAF | Ionian Sea, off Santa Maria di Leuca |
|---|
| June 29 | Regia Marina | '''Uebi Sciebeli''' | '''Adua''' class submarine | Sunk by 'HMS ''Dainty''' and 'HMS ''Ilex''' | West of Crete |
|---|
| July 1 | | '''Unterseeboot 26''' | Submarine | Sunk by the corvette 'HMS ''Gladiolus''' and a Royal Australian Air Force Short Sunderland | Atlantic Ocean near Ireland |
|---|
| July 1 | | '''Unterseeboot 102''' | Submarine | Sunk by 'HMS ''Vansittart' | South-west of Ireland |
|---|
| July 3 | | '''Bretange''' | '''Bretagne''' class battleship | Sunk at the attack on Mers-el-Kébir | Mers-el-Kébir, French North Africa |
|---|
| July 4 | | '''Rigault de Genouilly''' | '''Bougainville ''' class colonial sloop | Torpedoed and sunk by RN sub 'HMS ''Pandora' | North of Matifou, French North Africa |
|---|
| July 5 | | 'HMS ''Whirldwind''' | '''W''' class destroyer | Torpedoed and sunk by U-34 | South-west of Ireland |
|---|
| July 5 | Regia Marina | '''Zeffiro''' | '''Turbine''' class destroyer | Sunk by Fairey Swordfish torpedo bombers from 'HMS ''Eagle''' | Tobruk |
|---|
| July 6 | | 'HMS ''Shark''' | '''S''' class submarine | Sunk under tow by German minesweeping trawlers '''M-1803''', '''M1806''' and '''M-1807''' after capture by German seaplanes the previous day | West-south-west of Egersund |
|---|
| July 9 | | 'HMS ''Salmon''' | '''S''' class submarine | Lost, probably sunk by a mine | Off Norway |
|---|
| July 11 | | 'HMS ''Escort''' | '''E''' class destroyer | Torpedoed by the Italian submarine '''Guglielmo Marconi''' on July 8, sank under tow July 11 | East of Gibraltar |
|---|
| July 16 | | 'HMS ''Imogen''' | '''I''' class destroyer | Accidentally rammed and sunk by cruiser 'HMS ''Glasgow''' | Off Duncasby Head, Scotland |
|---|
| July 16 | | 'HMS ''Phoenix''' | '''Parthian''' class submarine | Sunk by the Italian torpedo boat '''Albatros''' | Off Augusta, Sicily |
|---|
| July 19 | Regia Marina | '''Bartolomeo Colleoni''' | '''Condottieri class''' cruiser | Sunk by RAN and RN ships in the Battle of Cape Spada | Off Cape Spada, Crete |
|---|
| July 20 | | HMS '''Brazen''' | '''B''' class destroyer | Sunk by air attack | Off Dover |
|---|
| July 20 | Regia Marina | '''Nembo''' | '''Turbine''' class destroyer | Sunk by Fairey Swordfish torpedo bombers from 'HMS ''Eagle''' | Gulf of Bomba, near Tobruk |
|---|
| July 20 | Regia Marina | '''Ostro''' | '''Turbine''' class destroyer | Sunk by Fairey Swordfish torpedo bombers from 'HMS ''Eagle''' | Gulf of Bomba, near Tobruk |
|---|
| July 26 | | '''Luchs''' | '''1924 Raubtier''' class torpedoboat | Torpedoed and sunk by RN submarine 'HMS ''Swordfish''' | North Sea, off Norway |
|---|
| July 27 | | 'HMS ''Codrington''' | '''A''' class destroyer leader | Sunk by air attack | Off Dover |
|---|
| July 27 | | 'HMS ''Wren''' | '''W''' class destroyer | Sunk by German bombers | Off Aldeburgh, England |
|---|
| July 30 | | 'HMS ''Delight''' | '''D''' class destroyer | Sank in port after being damaged by German bombers the previous day | Portland harbour |
|---|
| July 30 | | 'HMS ''Narwhal''' | '''Grampus''' class submarine | Sunk by German aircraft | Off Norway |
|---|
| August 1 | | 'HMS ''Oswald''' | '''Odin''' class submarine | Rammed and sunk by the Italian Navigatori class destroyer '''Ugolino Vivaldi''' | South of Cape Spartivento, Strait of Messina |
|---|
| August 1 | | 'HMS ''Spearfish''' | '''S''' class submarine | Torpedoed and sunk by '''U-34''' | North-east of Aberdeen, Scotland |
|---|
| August 1 | | '''U-25''' | Submarine | Sunk by minefield | North Sea near Terchelling |
|---|
| August 3 | | 'HMS ''Thames''' | '''River''' class submarine | Probably mined | North Sea |
|---|
| August 10 | | 'HMS ''Transylvania''' | Armed merchant cruiser | Torpedoed and sunk by German uboat '''U-56''' | Northwest of Malin Head, Donegal |
|---|
| August 15 | | '''Elli''' | Light cruiser | Torpedoed and sunk by Italian submarine '''Delfino''' | Aegean Sea, off Tinos |
|---|
| August 20 | | '''Unterseeboot 51''' | Submarine | Sunk by submarine 'HMS ''Cachalot''' | West of St. Nazaire |
|---|
| August 22 | Regia Marina | '''Iride''' | 600-Serie '''Perla''' class submarine | Sunk by Fairey Swordfish torpedo bomber from 'HMS ''Eagle''' | Gulf of Bomba off Cyrenaica |
|---|
| August 23 | | 'HMS ''Hostile''' | '''H''' class destroyer | Damaged by mine, scuttled by 'HMS ''Hero''' | Off Cape Bon in the Strait of Sicily |
|---|
| August 24 | | 'HMS ''Penzance''' | '''Folkestone''' class sloop | Torpedoed and sunk by U-37 | South-west of Iceland |
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| August 28 | | 'HMS ''Dunvegan Castle''' | Armed merchant cruiser | Torpedoed by '''U-46''' August 27, floundered the next day | West of Ireland |
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| August 31 | | 'HMS ''Esk''' | '''E''' class destroyer | Sunk by mine | Off Texel, the Netherlands |
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| September 1 | | 'HMS ''Ivanhoe''' | '''I''' class destroyer | Sunk by mine | North Sea, off the Frisian Islands |
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| September 3 | | '''Unterseeboot 57''' | Submarine | Collision with Norwegian steamship '''Rona''' | Off Brunsbüttel, Schleswig-Holstein |
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| September 15 | | 'HMS ''Dundee''' | '''Shoreham''' class sloop | Torpedoed and sunk by U-48 while acting as convoy escort | West of Ireland |
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| September 17 | Regia Marina | '''Aquilone''' | '''Turbine''' class destroyer | Sunk by Fairey Swordfish torpedo bombers from 'HMS ''Illustrious''' | Benghazi harbor |
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| September 17 | Regia Marina | '''Borea''' | '''Turbine''' class destroyer | Sunk by Fairey Swordfish torpedo bombers from 'HMS ''Illustrious''' | Benghazi harbor |
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| September 23 | | '''L'Audacieux''' | Destroyer | Beached after being attacked by 'HMAS ''Australia''' during the Battle of Dakar | Dakar, French West Africa |
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| September 23 | | '''Persée''' | '''Redoutable''' class submarine | Sunk during by 'HMS ''Foresight''' and 'HMS ''Inglefield''' during the Battle of Dakar | Off Dakar |
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| September 24 | | '''Ajax''' | '''Redoutable''' class submarine | Sunk during by 'HMS ''Fortune''' during the Battle of Dakar | Off Dakar |
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| September 24 | | '''Ostmark''' | Light seaplane tender | Sunk by the Royal Navy submarine 'HMS ''Tuna''' | Bay of Biscay south-west of St. Nazaire |
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| September 30 | Regia Marina | '''Gondar''' | '''Adua''' class submarine | Sunk by 'HMAS ''Stuart''' and a Short Sunderland flying boat | Off Alexandria |
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| October 2 | Regia Marina | '''Berillo''' | '''Perla''' class submarine | Scuttled after attack from RN destroyers 'HMS ''Havock''' and 'HMS ''Hasty''' | Off Sidi Barrani |
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| October 4 | | 'HMS ''Rainbow''' | '''R''' class submarine | Rammed and sunk by the Italian merchant ''Antonietta Costa'' | Off Bari |
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| October 12 | Regia Marina | '''Artigliere''' | '''Soldati''' class destroyer | Sunk by 'HMS ''York''' after having been heavily damaged by 'HMS ''Ajax''' | Ionian Sea |
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| October 15 | | 'HMS ''Triad''' | '''T''' class submarine | Sunk in surface gunbattle with the Italian submarine '''Enrico Toti''' | Gulf of Taranto |
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| October 17 | | 'HMS ''Dundalk''' | '''Hunt''' class minesweeper | Struck mine October 16, foundered the next day while under tow | Off Harwich |
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| October 18 | Regia Marina | '''Durbo''' | '''Adua''' class submarine | Sunk by 'HMS ''Firedrake''', 'HMS ''Wrestler''' and two Saunders-Roe London flying boats of No. 202 Squadron RAF | East of Gibraltar |
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| October 18 | | 'HMS ''H49''' | '''H''' class submarine | Deptcharged and sunk by the German submarine chasers '''UJ 116''' and '''UJ 118''' | Off Texel |
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| October 19 | | 'HMS ''Venetia''' | '''V''' class destroyer | Mined | Off Margate |
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| October 20 | Regia Marina | '''Lafolè''' | '''Adua''' class submarine | Sunk by 'HMS ''Gallant''', 'HMS ''Griffin''' and 'HMS ''Hotspur''' | North of Melilla |
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| October 20 | Regia Marina | '''Francesco Nullo''' | '''Sauro''' class destroyer | Beached following surface action with 'HMS ''Kimberley''' and 'HMNZS ''Leander''', wreck destroyed by three RAF Bristol Blenheim bombers the following day | Near Massawa |
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| October 22 | | 'HMCS ''Margaree''' | '''River''' class destroyer | Sunk after collision with freighter 'M.V. ''Port Fairy''' | North Atlantic |
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| October 28 |  25 px British Merchant Navy | '''Empress of Britain''' | Steam passenger ship | Torpedoed and sunk by '''U-32''' | Northwest of Ireland |
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| October 30 | | 'HMS ''Sturdy''' | '''S''' class destroyer | Ran aground and was totally wrecked | Off Tiree Island, Scotland |
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| October 30 | | '''Unterseeboot 32''' | Submarine | Sunk by 'HMS ''Harvester''' and 'HMS ''Highlander''' | Northwest of Ireland |
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| October 31 | Regia Marina | '''Faà di Bruno''' | '''Marcello''' class Submarine | Lost to unknown reasons | Atlantic |
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| November 2 | | '''Unterseeboot 31''' | Submarine | Sunk by 'HMS ''Antelope''' | North-west of Ireland |
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| November 3 | | 'HMS ''Laurentic''' | Armed merchant cruiser | Torpedoed and sunk by '''U-99''' | West of Bloody Foreland, Ireland |
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| November 5 | | 'HMS ''Jervis Bay''' | Armed merchant cruiser | Sunk by German pocket battleship '''Admiral Scheer''' | Mid-Atlantic |
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| November 7 | | 'HMS ''Swordfish''' | '''S''' class submarine | Sunk by mine | South of St. Catherine’s Head, Isle of Wight |
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| November 7 | | '''T6''' | '''Type 1935''' class torpedoboat | Sunk by mine | Off Kinnaired Head, near Aberdeen, Scotland |
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| November 8 | | 'HNoMS ''Fridtjof Nansen''' | Offshore Patrol Vessel | Ran aground on an unmarked shallow and sank | Off Jan Mayen |
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| November 8 | | '''Poncelet''' | Submarine | Sunk by 'HMS ''Milford''' during the Battle of Gabon | Gabon, French Equatorial Africa |
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| November 9 | | '''Bougainville''' | '''Bougainville''' class colonial sloop | Sunk by Free French naval forces during the Battle of Gabon | Gabon, French Equatorial Africa |
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| November 11 | Regia Marina | '''Conte di Cavor''' | '''Conte di Cavour''' class battleship | Sunk by Fairey Swordfish torpedo bombers from 'HMS ''Illustrious''' during the battle of Taranto | Taranto, Italy |
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| November 19 |  22x20px Royal Netherlands Navy | '''O 22''' | '''O 21''' class submarine | Sunk, probably by mine | South-west of Norway |
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| November 19 | | '''Unterseeboot 104''' | Submarine | Disappeared, possibly lost to mine field off Tory Island | North-west of Ireland |
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| November 26 | | 'HMS ''Regulus''' | '''R''' class submarine | Most likely mined | Straits of Taranto |
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| November 27 | | 'HMS ''Port Napier''' | Minelayer | Sunk by explosion after accidental fire the previous day | Kyle of Lochalsh |
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| December 2 | | 'HMS ''Forfar''' | Armed merchant cruiser | Sunk by '''U-99''' | Atlantic, west of Ireland |
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| December 5 | | 'HMS ''Cameron''' | '''Town''' class destroyer | Bombed and wrecked by the Luftwaffe while in drydock | Portsmouth |
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| December 14 | Regia Marina | '''Naiade''' | '''Sirena''' class submarine | Sunk by RN destroyers 'HMS ''Hyperion''' and 'HMS ''Hereward''' | Off Bardia, Libya |
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| December 15 | Regia Marina | '''Capitano Tarantini''' | '''Liuzzi''' class submarine | Torpedoed and sunk by RN submarine 'HMS ''Thunderbolt''' | Gironde estuary, France |
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| December 15 | Forces navales françaises libres | '''Narval''' | '''Requin''' class submarine | Lost to mine | Off Sfax, French North Africa |
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| December 17 | | 'HMS ''Acheron''' | '''A''' class destroyer | Sunk by mine | Off the Isle of Wight |
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| December 18 | | 'HMS ''Triton''' | '''T''' class submarine | Lost to either mines or Italian torpedo boats | Strait of Otranto |
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| December 19 | | '''Sfax''' | '''Agosta''' class submarine | Torpedoed and sunk, together with 2,785 ton fleet oiler '''Rhône''', by U-37 due to mistaken identity | Off Cape Juby, French North Africa |
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| December 22 | | 'HMS ''Hyperion''' | '''H''' class destroyer | Sunk by mine | Off Pantelleria east of Cape Bon in the Strait of Sicily |
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| December 29 | | '''Proteus''' | Submarine | Sunk by Italian '''Spica''' class torpedo boat '''Antares''' shortly after having torpedoed and sunk the 11,452 ton Italian troop transport '''Sardegna''' | Southern Adriatic, east of Brindisi |
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