Editing Convoy (section)

===World War II===
{{See also|Convoys in World War II}}

====Atlantic====
{{see also|Battle of the Atlantic}}
[[File:Convoy routes 1941.jpg|thumb|Convoy routes in the Atlantic Ocean during 1941]]
[[File:Allied convoy underway in the Atlantic Ocean near Iceland, circa in 1942 (80-G-72409).jpg|thumb|Allied convoy near Iceland, 1942]]
[[File:Convoy in Bedford Basin, Nova Scotia Convoi dans le bassin de Bedford (Nouvelle Écosse) (8640015819).jpg|thumb|Allied convoy in [[Bedford Basin]], Nova Scotia on 1 April 1943]]
The British adopted a convoy system, initially voluntary and later compulsory for almost all merchant ships, the moment that [[World War II]] was declared. Each convoy consisted of between 30 and 70 mostly unarmed merchant ships.<ref>[http://www.history.ca/ontv/titledetails.aspx?titleid=248473 Convoy] {{webarchive|url=https://web.archive.org/web/20110719201429/http://www.history.ca/ontv/titledetails.aspx?titleid=248473 |date=2011-07-19 }} from ''History Television.''</ref> Canadian, and later American, supplies were vital for Britain to continue its war effort. The course of the [[Battle of the Atlantic]] was a long struggle as the Germans developed anti-convoy tactics and the British developed counter-tactics to thwart the Germans.

The capability of a heavily armed warship against a convoy was dramatically illustrated by the fate of [[Convoy HX 84]]. On November 5, 1940, the German heavy cruiser {{ship|German cruiser|Admiral Scheer||2}} encountered the convoy. ''Maiden'', ''Trewellard'', and ''Kenbame Head'' were quickly destroyed, and  ''Beaverford'' and ''Fresno City'' falling afterwards. Only the sacrifices of the [[Armed Merchant Cruiser|armed merchant cruiser]] {{HMS|Jervis Bay|F40|6}} and the freighter ''Beaverford'' to stall the ''Scheer'', in addition to failing light, allowed the rest of the convoy to escape.

The deterrence value of a battleship in protecting a convoy was also dramatically illustrated when the German light battleships (referred by some as battlecruisers) {{ship|German battleship|Scharnhorst||2}} and {{ship|German battleship|Gneisenau||2}}, mounting {{convert|11|in|cm|abbr=on}} guns, came upon an eastbound British convoy ([[Convoy HX 106|HX 106]], with 41 ships) in the North Atlantic on February 8, 1941. When the Germans detected the slow but well-protected battleship {{HMS|Ramillies|07|6}} escorting the convoy, they fled the scene rather than risk damage from her {{convert|15|in|cm|abbr=on}} guns.

The enormous number of vessels involved and the frequency of engagements meant that statistical techniques could be applied to evaluate tactics: an early use of [[operational research]] in war.

Prior to overt participation in World War II, the US was actively engaged in convoys with the British in the North Atlantic Ocean, primarily supporting British activities in Iceland.<ref>{{Cite book|title=The Western Hemisphere, Guarding the United States and Its Outposts|last=Conn|first=Stetson|publisher=Office of the Chief of Military History, Department of the Army. US Government Printing Office|year=1964|location=Washington, D.C.|pages=470}}</ref>

After Germany declared war on the US, the US Navy decided not to organize convoys on the American eastern seaboard. US Fleet Admiral [[Ernest King]] ignored advice on this subject from the British, as he had formed a poor opinion of the Royal Navy early in his career. The result was what the U-boat crews called their [[Second Happy Time]], which did not end until convoys were introduced.<ref name="Oxford_Companion_online" />{{CN|date=September 2021}}

====Pacific====
{{See also|Pacific War}}
In the Pacific Theater of World War II, [[Japan]]ese merchant ships rarely traveled in convoys. Japanese destroyers were generally deficient in antisubmarine weaponry compared to their Allied counterparts, and the Japanese navy did not develop an inexpensive convoy escort like the Allies' [[destroyer escort]]/[[frigate]] until it was too late. In the early part of the conflict, American submarines in the Pacific were ineffective as they suffered from timid tactics, faulty torpedoes, and poor deployment, while there were only small numbers of British and Dutch boats. U.S. Admiral [[Charles A. Lockwood]]'s efforts, coupled with strenuous complaints from his captains, rectified these problems and U.S. submarines became much more successful by war's end. As a result, the Japanese merchant fleet was [[Allied submarines in the Pacific War|largely destroyed]] by the end of the war. Japanese submarines, unlike their U.S. and German equivalents, focused on U.S. battle fleets rather than merchant convoys, and while they did manage some early successes, sinking two U.S. carriers, they failed to significantly inhibit the invasion convoys carrying troops and equipment in support of the U.S. island-hopping campaign.<ref name="Oxford_Companion_online" />

Several notable battles in the South Pacific involved Allied bombers interdicting Japanese troopship convoys which were often defended by Japanese fighters, notable [[Naval Battle of Guadalcanal#Other actions.2C November 13.E2.80.9314|Guadalcanal]] (13 November 1942), [[Kenneth Walker (general)#Rabaul 5 January 1943|Rabaul]] (5 January 1943), and the [[Battle of the Bismarck Sea]] (2–4 March 1943).

At the [[Battle off Samar]], the effectiveness of the U.S. Navy's escorts was demonstrated when they managed to defend their troop convoy from a much larger and more powerful Japanese battle-fleet. The Japanese force comprised four battleships and numerous heavy cruisers, while the U.S. force consisted of escort carriers, destroyers, and destroyer escorts. Large numbers of American aircraft (albeit without much anti-ship ordnance other than torpedoes) and aggressive tactics of the destroyers (with their radar-directed gunfire) allowed the U.S. to sink three Japanese heavy cruisers at the cost of one escort carrier and three destroyers.

====Tactics====
[[Image:Convoy_WS-12_en_route_to_Cape_Town,_1941.jpg|thumb|A convoy of merchant ships protected by airplanes ''en route'' to [[Cape Town]] during [[World War II]]]]
The German anti-convoy [[Naval tactics in the Age of Steam|tactics]] included:
* long-range surveillance aircraft to find convoys;
* strings of U-boats ([[Wolfpack (naval tactic)|wolfpack]]s) that could be directed onto a convoy by radio;
* breaking the British naval codes;
* improved anti-ship weapons, including magnetic detonators and sonic homing torpedoes.

The Allied responses included:
* [[airstrike|air raids]] on the U-boat bases at [[Brest, France|Brest]] and [[La Rochelle]];
* converted merchant ships, e.g., [[Merchant aircraft carrier]]s, [[CAM ship|Catapult Aircraft Merchantman]] and [[Armed merchantmen#Armed merchant cruisers|armed merchant cruisers]]
* [[Q-ship]]s, submarine-hunters disguised as unarmed merchant ships to lure submarines into an attack
* more convoy escorts, including cheaply produced yet effective [[destroyer escorts]]/[[frigate]]s (as [[corvette]]s were meant as a stopgap),  and [[escort aircraft carrier|escort carrier]]s;
* fighter aircraft (carried by escort carriers and merchant aircraft carriers) that would drive off German bombers and attack U-boats
* long-range aircraft patrols to find and attack U-boats;
* improved anti-submarine weapons such as the [[hedgehog (weapon)|hedgehog]];[[File:A convoy conference in progress, August 1942. A11796.jpg|thumb|A convoy conference in progress, August 1942]]
* larger convoys, allowing more escorts per convoy as well as the extraction of enough escorts to form hunter-killer support groups that were not attached to a particular convoy
* allocating vessels to convoys according to speed, so that faster ships were less exposed.

They were also aided by
* improved [[sonar]] ([[Sonar|ASDIC]]) allowing escort vessels to better track U-boats;
* breaking the [[Enigma machine|German naval cipher]];
* improved [[radar]] and [[radio direction finding]] allowing planes to find and destroy U-boats;
* improved escort anti-submarine tactics developed by the [[Western Approaches Tactical Unit]]<ref>{{Cite web|url=https://www.historic-uk.com/HistoryUK/HistoryofBritain/Wrens-Wargames-North-Atlantic/|title=Wrens, Wargames and the Battle of the Atlantic|website=Historic UK}}</ref><ref>Parkin, Simon (2020) "A Game of Birds and Wolves: The Ingenious Young Women Whose Secret Board Game Helped Win World War II." Little, Brown and Company</ref>

====Convoy battles====
[[File:80-G-24824 (21739024443).jpg|thumb|The covering forces of the [[Convoy PQ 17]] at anchor in the harbor at [[Hvalfjord]], Iceland, 1942]]
Many naval battles of World War II were fought around convoys, including:
* [[Convoy PQ 16]], May 1942
* [[Convoy PQ 17]], June–July 1942
* [[Convoy PQ 18]], September 1942
* [[Operation Pedestal]], August 1942
* The [[Naval Battle of Guadalcanal]], November 1942
* The [[Battle of the Barents Sea]], December 1942
* The [[Battle of the Bismarck Sea]], March 1943

The convoy prefix indicates the route of the convoy. For example, 'PQ' would be Iceland to Northern Russia and 'QP' the return route.