This outlines of some of the key events relating to the war at sea and merchant shipping in the Second World War, focussing on New Zealand involvement.
- 26 August: Admiralty (United Kingdom) assumes control of all British merchant shipping in anticipation of war.
- 1 September: Following Germany's invasion of Poland, New Zealand government issues emergency regulations to assume control of shipping in local waters.
- 3 September: Britain, France, Australia and New Zealand declare war on Germany; the Battle of the Atlantic begins. The British liner Athenia is torpedoed by U-30 off Ireland, and over 100 lives are lost.
- 4 September: Admiralty orders the introduction of convoy system for merchant ships.
- 21 October: Union Steam Ship Co (USSCo) liner Monowai is taken over by the New Zealand Division of the Royal Navy for conversion into an armed merchant cruiser (AMC).
- 14 December: British tanker Inverlane is mined in North Sea; among the victims is cook Leslie Yates – probably the first New Zealand merchant seafarer lost to enemy action during the war.
- 17 December: After sinking nine merchant ships in the South Atlantic and the Indian Ocean and fleeing an engagement with three British cruisers (including New Zealand-manned HMS Achilles), German pocket battleship Admiral Graf Spee is scuttled in River Plate, South America.
- 5 January: 1st Echelon of the 2 NZEF leaves New Zealand for the Middle East aboard the troop ships Empress of Canada, Strathaird, Orion, Rangitata, Dunera and Sobieski.
- 31 March: Atlantis, first of the nine German auxiliary cruisers or disguised merchant raiders, sails from Germany to harass Allied shipping. Over the next three and a half years raiders sink or capture over 140 merchant ships.
- 2 May: 2nd Echelon of the 2 NZEF sails from New Zealand aboard Aquitania, Empress of Britain, Empress of Japan and Andes.
- 26 May: Start of evacuation of troops from Dunkirk, northern France, involving numerous merchant ships; 338,000 personnel are evacuated by 4 June.
- 10 June: Italy joins the war against Britain and France, threatening Mediterranean and Suez shipping routes.
- 13–14 June: German raider Orion enters New Zealand waters undetected and lays 228 contact mines in northern and eastern approaches to the Hauraki Gulf.
- 17 June: British liner Lancastria, evacuating troops from St Nazaire, France, is sunk by German bombers. Around 3000 lives are lost, but over 200,000 Allied personnel are safely evacuated from Biscay ports.
- 19 June: Orion's mines sink the liner Niagara (owned by Canadian-Australasian Line, managed by the USSCo) off the Northland coast; all 349 passengers and crew are rescued.
- 25 June: The fall of France; German U-boats soon begin operating from bases on the French Atlantic coast, greatly enhancing their operational range and patrol duration.
- 10 July: Battle of Britain begins with German air attacks on English Channel convoys.
- 20 August: New Zealand Shipping Co (NZSCo) freighter Turakina sunk by German raider Orion in Tasman Sea, 260 miles west of Taranaki; 36 crew were killed, and 20 survivors were taken prisoner.
- 30 August: After a lengthy refit, the Monowai is commissioned as an AMC and is manned by a mixture of naval regulars, reservists and merchant seamen.
- 10 September: Following heavy German bombing, the Port of London is closed to ocean-going ships; traffic is diverted to Glasgow, Liverpool, Cardiff and other west-coast ports.
- 25 November: Holm Shipping Co steamer Holmwood is captured and sunk by raiders Orion and Komet near the Chatham Islands; 29 crew and passengers are taken prisoner.
- 27 November: NZSCo liner Rangitane is sunk by Orion and Komet 300 miles off New Zealand's East Cape; 15 passengers and crew are killed, and around 300 are taken prisoner. This is the largest ship sunk by German raiders in the Second World War.
- 8 December: USSCo freighter Komata is sunk by the Komet off Nauru Island; two crew are killed.
- 21 December: German Pacific raiders release about 500 captives on Emirau Island, Bismarck Archipelago, near New Guinea.
- 10 January: USSCo liner Maunganui is taken over by the New Zealand government for conversion into a hospital ship.
- 16 January: Shaw Savill & Albion (SS&A) liner Zealandic is torpedoed by U-106 in the North Atlantic. All hands are lost, including at least six New Zealand seamen.
- 14 May: Orion's mines claim a second victim in the Hauraki Gulf – the minesweeper HMS Puriri, a former Anchor Co coaster, is sunk with the loss of five crew (all ex-merchant seamen reservists).
- 22 May: Maunganui arrives in Egypt to repatriate the first group of 2 NZEF patients.
- 12 August: First merchant convoy leaves the United Kingdom for the Russian Arctic via Iceland, and it arrives in Archangel on 31 August.
- 27 October: USSCo liner Awatea leaves Vancouver for Hong Kong with 2000 Canadian troops; later it evacuates women and children from Singapore.
- 19 November: German raider Kormoran and Australian cruiser HMAS Sydney are both sunk during an engagement off Western Australia; none of Sydney's 645 crew survive.
- 9 December: Panamanian-flagged MV Donerail is sunk by Japanese submarine I-10 near Hawaii. A total of 32 lives are lost, including purser John Rendle who was almost certainly the first New Zealander killed in the Pacific War.
- 10 December: Battleship HMS Prince of Wales and battlecruiser Repulse are sunk by Japanese bombers in the South China Sea.
- 11 January: German U-boats begin attacks along the United States' eastern seaboard and in the Caribbean/Gulf of Mexico; almost 400 ships are sunk in six months, before an effective convoy system is established.
- 16 January: HMNZS Monowai, escorting Taroona, fights an inconclusive gunnery duel with Japanese submarine I-20 off Suva.
- 15 February: Singapore falls to the Japanese.
- 19 February: Japanese air raid on Darwin, northern Australia, sinks eight ships and kills about 250, including New Zealander Harold Humphrey, a steward on the hospital ship Mununda.
- 3 March: USSCo freighter Narbada evades attack by Japanese submarine I-3 off Fremantle.
- 4 July: Fearing an attack by the German battleship Tirpitz, Admiralty orders merchant ships of the Arctic convoy PQ17 to scatter; as a result, 24 out of 37 are sunk by U-boats and bombers.
- 11 July: Port Line freighter Port Hunter is torpedoed by U-582 off West Africa; 88 lives are lost, including at least seven New Zealand seamen, two of whom were aged 15.
- 12 July: USSCo freighter Hauraki, bound for Egypt, is captured in the Indian Ocean by Japanese AMCs Aikoku Maru and Hokuku Maru; 55 crew are taken prisoner.
- 15 August: Arrival in Valletta of the damaged tanker Ohio and other survivors of the Operation Pedestal convoy helps to ensure Malta's survival. Nine of the convoy's 14 merchant ships were sunk, including SS&A's Wairangi and Waimarama; four New Zealand seamen on the latter vessel are killed.
- 22 August: Awatea, loaded with Canadian troops, collides with the destroyer USS Buck in a convoy off Newfoundland; both ships are saved, but in the confusion, USS Ingraham collides with the navy tanker USS Chemung and sinks with the loss of about 250 lives.
- 30 August: Richardson & Co coaster Kopara, under charter to the United States Navy, survives a Japanese air raid off Guadalcanal, Solomon Islands; later commissioned as USS Kopara, the ship serves with American Pacific forces until 1945.
- 8 November: Awatea lands 3000 assault troops near Algiers during Operation Torch, the Allied invasion of Vichy-French North Africa.
- 11 November: Awatea is attacked and disabled by German bombers off Bougie (Bejaia), Algeria, but all 150 crew are rescued; the wreck is later sunk by Italian submarine Argo.
- 7 December: SS&A liner Ceramic is torpedoed in the North Atlantic by U-515, and 655 passengers and crew are lost (including at least four New Zealand seamen).
- 18 January: USSCo freighter Kalingo is torpedoed by Japanese sub I-21, 60 miles east of Sydney; two crew are lost.
- 16–19 March: German wolf packs attack North Atlantic convoys HX229 and SC122 in the greatest convoy battle of war: 22 merchant ships are sunk, including Blue Star's Canadian Star, from which three New Zealand seamen are lost.
- 20 March: I-27 sinks British freighter Fort Mumford in the Indian Ocean and machine-guns lifeboats, killing 50 crew, including at least five New Zealand seamen.
- 26 April: USSCo freighter Limerick is torpedoed by I-177 off Cape Byron, NSW; two crew are lost.
- 14 May: Australian hospital ship Centaur is torpedoed by I-177 off the Queensland coast with the loss of 268 lives. This is the Tasman Sea's worst maritime disaster.
- 24 May: Turning point in Battle of the Atlantic: after suffering heavy losses against stronger Allied escort forces, Admiral Dönitz orders the temporary withdrawal of German wolf packs from the North Atlantic. A total of 41 U-boats are sunk in the month.
- 18 June: Monowai decommissioned from Royal NZ Navy; reverts to merchant service under control of the British Ministry of War Transport.
- 10 July: Allied invasion of Sicily begins, supported by a large fleet of merchant ships.
- 9 September: Allies land at Salerno on Italian mainland.
- 17 October: Last German raider still at sea, Michel, is sunk by a United States submarine off Japan.
- 26 November: Troop ship Rohna is sunk in the Mediterranean by a German glider bomb (radio-guided missile); over 1000 United States troops are killed.
- 2 December: German air raid on Bari, Italy, destroys 17 Allied merchant ships, and more than 1000 lives are lost.
- 26 December: Battle of North Cape: German battlecruiser Scharnhorst is sunk by Royal Navy warships covering Arctic convoy JW55.
- 6 January: Underwood (built for the USSCo but requisitioned by the British Ministry of War Transport on completion in the United Kingdom in 1941) is sunk by an E-boat in the English Channel.
- 22 January: Allied amphibious landings occur behind German lines at Anzio, Italy.
- 12 February: British troop ship Khedive Ismail is sunk by I-27 in the Indian Ocean with the loss of 1300 lives.
- 17 February: Japanese transport Hoki Maru, formerly USSCo's Hauraki, is sunk by United States torpedo bombers at Truk, Caroline Islands.
- 14 April: Explosion of British ammunition ship Fort Stikine in Bombay Harbour destroys 11 ships and kills at least 800 people.
- 6 June: D-Day: over 800 merchant ships, including the Monowai, which lands 1800 troops at 'Gold' beach, are involved in the Normandy landings. This is the first of 45 English Channel crossings that the Monowai makes, carrying a total of 73,000 troops.
- 15 August: Allied landings are made in the south of France, supported by a large fleet of merchant ships.
- 7 January: German submarine U-862 enters New Zealand waters and cruises, undetected, down the east coast of the North Island.
- 30 January: German liner Wilhelm Gustloff, evacuating refugees, military personnel and wounded from East Prussia, is sunk in the Baltic by Soviet submarine S-13. The estimated death toll is 8500. This is the worst shipping disaster in history.
- 17 March: Hospital ship Maunganui is sent to join the British Pacific fleet train at Manus Island, near New Guinea. It is later deployed to Leyte Gulf, the Philippines.
- 22 April: Monowai sails from the United Kingdom for Odessa on the Black Sea, carrying 1600 Soviet ex-POWs; other repatriation voyages between Odessa, Marseilles and Bombay follow.
- 7 May: U-2336 torpedoes a Norwegian and a Canadian merchant ship off Scotland. These are the last vessels sunk by U-boats during the war because German surrender signals the end of the Battle of the Atlantic.
- 12 May: Last Arctic convoy sails from the United Kingdom for the Soviet Union.
- 10 August: Hauraki POW William Brodie dies of injuries sustained during the Allied shelling of Kamaishi, northern Japan. He is the fifth of the ship's crew to die in Japanese captivity.
- 15 August: Japan surrenders.
- 13 September: Monowai sails from Singapore with 850 British ex-POWs, and arrives in Liverpool on 8 October.
- 23 November: Maunganui begins its last voyage as a hospital ship, repatriating POWs from the Far East to the United Kingdom and returning with the last 2 NZEF invalids. It arrives in New Zealand on 20 March 1946, having carried 5677 patients since 1941.
Merchant Navy Day
In Britain, New Zealand and other Commonwealth countries, 3 September is Merchant Navy Day. The date commemorates the sinking of the first British merchant ship in 1939, just hours after war was declared. Merchant seafarers were involved in the Second World War from the first day to the last.