Convoys in World War I
The convoy
A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support, though it may also be used in a non-military sense, for example when driving through remote areas.-Age of Sail:Naval...

—a group of merchantmen
Cargo ship
A cargo ship or freighter is any sort of ship or vessel that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year; they handle the bulk of international trade...

 or troopship
A troopship is a ship used to carry soldiers, either in peacetime or wartime...

s travelling together with a naval escort—was revived during World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

(1914–18), after having been discarded at the start of the Age of Steam
Naval tactics in the Age of Steam
The development of the steam ironclad firing explosive shells in the mid 19th century rendered sailing tactics obsolete. New tactics were developed for the big-gun Dreadnought battleships. The mine, torpedo, submarine and aircraft posed new threats, each of which had to be countered, leading to...

. Although convoys were used by the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 in 1914 to escort troopships from the Dominions, and in 1915 by both it and the French Navy
French Navy
The French Navy, officially the Marine nationale and often called La Royale is the maritime arm of the French military. It includes a full range of fighting vessels, from patrol boats to a nuclear powered aircraft carrier and 10 nuclear-powered submarines, four of which are capable of launching...

 to cover their own troop movements for overseas service, they were not systematically employed by any belligerent navy until 1916. The Royal Navy was the major user and developer of the modern convoy system, and regular transoceanic convoying began in June 1917. They made heavy use of aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 for escorts, especially in coastal waters, an obvious departure from the convoy practices of the Age of Sail
Age of Sail
The Age of Sail was the period in which international trade and naval warfare were dominated by sailing ships, lasting from the 16th to the mid 19th century...


As historian Paul E. Fontenoy put it, "[t]he convoy system defeated the German submarine campaign
U-boat Campaign (World War I)
The U-boat Campaign from 1914 to 1918 was the World War I naval campaign fought by German U-boats against the trade routes of the Entente Powers...

." From June 1917 on, the Germans were unable to meet their set objective of sinking 600000 LT (609,630 t) of enemy shipping per month. In 1918, they were rarely able to sink more than 300000 LT (304,815 t). Between May 1917 and the end of the war on 11 November 1918, only 154 of 16,539 vessels convoyed across the Atlantic had been sunk, of which 16 were lost through the natural perils of sea travel and a further 36 because they were stragglers.


The first large convoy of the war was the Australian and New Zealand Army Corps
Australian and New Zealand Army Corps
The Australian and New Zealand Army Corps was a First World War army corps of the Mediterranean Expeditionary Force that was formed in Egypt in 1915 and operated during the Battle of Gallipoli. General William Birdwood commanded the corps, which comprised troops from the First Australian Imperial...

 (ANZAC) convoy. On 18 October 1914, the Japanese
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...

Battlecruisers were large capital ships built in the first half of the 20th century. They were developed in the first decade of the century as the successor to the armoured cruiser, but their evolution was more closely linked to that of the dreadnought battleship...

  left the port of Wellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...

, New Zealand, with 10 troopships. It was met by 28 Australian ships and the Australian
Royal Australian Navy
The Royal Australian Navy is the naval branch of the Australian Defence Force. Following the Federation of Australia in 1901, the ships and resources of the separate colonial navies were integrated into a national force: the Commonwealth Naval Forces...

 light cruiser
Light cruiser
A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck...

 . The Japanese also sent the cruiser to patrol the Indian Ocean during the convoy′s crossing to Aden
Aden is a seaport city in Yemen, located by the eastern approach to the Red Sea , some 170 kilometres east of Bab-el-Mandeb. Its population is approximately 800,000. Aden's ancient, natural harbour lies in the crater of an extinct volcano which now forms a peninsula, joined to the mainland by a...

. During the crossing, HMAS Sydney was caught up in the Battle of Cocos
Battle of Cocos
The Battle of Cocos took place on 9 November 1914 during the First World War off the Cocos Islands, in the north east Indian Ocean. The German light cruiser attacked the British cable station on Direction Island and was engaged several hours later by the Australian light cruiser...

 (9 November), but the Japanese-escorted convoy reached Aden on 25 November. The Japanese continued to escort ANZAC convoys throughout the war. The convoys of Dominion troops were, weather permitting, escorted into port by airships.

With the advent of commerce raiding
Commerce raiding
Commerce raiding or guerre de course is a form of naval warfare used to destroy or disrupt the logistics of an enemy on the open sea by attacking its merchant shipping, rather than engaging the combatants themselves or enforcing a blockade against them.Commerce raiding was heavily criticised by...

 by the submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s of the Royal Navy, the Imperial Russian Navy
Imperial Russian Navy
The Imperial Russian Navy refers to the Tsarist fleets prior to the February Revolution.-First Romanovs:Under Tsar Mikhail Feodorovich, construction of the first three-masted ship, actually built within Russia, was completed in 1636. It was built in Balakhna by Danish shipbuilders from Holstein...

, and the Kaiserliche Marine
Kaiserliche Marine
The Imperial German Navy was the German Navy created at the time of the formation of the German Empire. It existed between 1871 and 1919, growing out of the small Prussian Navy and Norddeutsche Bundesmarine, which primarily had the mission of coastal defense. Kaiser Wilhelm II greatly expanded...

(Imperial German Navy), it was neutral Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, at the insistence of Germany, that first used a convoy system in early November 1915 to protect its own merchant shipping after the British and the Russians attacked its iron ore shipments to Germany. The German merchant fleet proposed a similar expedient, but the navy refused. However, in April 1916, Admiral Prince Heinrich of Prussia—commander-in-chief in the Baltic theater
British submarine flotilla in the Baltic
A British submarine flotilla operated in the Baltic Sea for three years during the First World War. The squadron of nine submarines was attached to the Russian Baltic Fleet. The main task of the flotilla was to prevent the import of iron ore from Sweden to Imperial Germany...

—approved regular scheduled escorts for German ships to Sweden. Losses to enemy submarines were drastically cut from the level of the previous year, and only five freighters were lost before the war′s end. In June 1916, the Baltic Fleet
Baltic Fleet
The Twice Red Banner Baltic Fleet - is the Russian Navy's presence in the Baltic Sea. In previous historical periods, it has been part of the navy of Imperial Russia and later the Soviet Union. The Fleet gained the 'Twice Red Banner' appellation during the Soviet period, indicating two awards of...

 attacked a German convoy in the Bråviken
Bråviken is a bay of the Baltic sea that is located near Norrköping in Östergötland, Sweden....

, destroying an auxiliary cruiser and some Swedish merchantmen, before mistakes by the commander of the Destroyer Division—Aleksandr Vasiliyevich Kolchak—allowed the majority of the convoy to escape back to Norrköping
Norrköping is a city in the province of Östergötland in eastern Sweden and the seat of Norrköping Municipality, Östergötland County. The city has a population of 87,247 inhabitants in 2010, out of a municipal total of 130,050, making it Sweden's tenth largest city and eighth largest...



To cover trade with the neutral Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, the British instituted their first regular convoy on 26 July 1916, from the Hook of Holland to Harwich
Harwich is a town in Essex, England and one of the Haven ports, located on the coast with the North Sea to the east. It is in the Tendring district. Nearby places include Felixstowe to the northeast, Ipswich to the northwest, Colchester to the southwest and Clacton-on-Sea to the south...

, a route targeted by the German U-boats based out of Flanders
Flanders is the community of the Flemings but also one of the institutions in Belgium, and a geographical region located in parts of present-day Belgium, France and the Netherlands. "Flanders" can also refer to the northern part of Belgium that contains Brussels, Bruges, Ghent and Antwerp...

. Only one straggler was lost before the Germans announced unrestricted submarine warfare
Unrestricted submarine warfare
Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchantmen without warning, as opposed to attacks per prize rules...

 on 1 February 1917, and only six after that before the war's end despite 1,861 sailings. The Holland convoys were sometimes referred to as the "Beef Trip" on account of the large proportion of food transported. They were escorted by destroyer
In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against smaller, powerful, short-range attackers. Destroyers, originally called torpedo-boat destroyers in 1892, evolved from...

s of the Harwich Force
Harwich Force
The Harwich Force was a squadron of the Royal Navy, formed during the First World War, that went on to play a significant role in the war.-History:...

 and, later in the war, by AD Flying Boat
AD Flying Boat
|-See also:-References:NotesBibliography*Andrews, C.F. and E.B. Morgan. Supermarine Aircraft since 1914. London:Putnam, 1987. ISBN 0-85177-800-3.*Bruce, J.M. British Aeroplanes 1914-18. London:Putnam, 1957....

s based out of Felixstowe
Felixstowe is a seaside town on the North Sea coast of Suffolk, England. The town gives its name to the nearby Port of Felixstowe, which is the largest container port in the United Kingdom and is owned by Hutchinson Ports UK...


The first convoys to sail after the German announcement were requested by the French Navy, desirous of defending British coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 shipments. The Royal Navy's first coal convoy crossed the Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...

 on 10 February. These convoys were more weakly escorted, and contained a mixture of both steam-powered ships and sailing ships, as well as escorting aircraft based on the coast. In all, only 53 ships were lost in 39,352 sailings. When shippers from Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

—the "neutral ally"—requested convoys in 1916 after a year of very serious losses, but refused to accept the routes chosen by the Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...

, they were declined. After the German proclamation, the Norwegians accepted British demands and informal convoying began in late January or February 1917, but regular convoys did not begin until 29 April. That same day, the first coastal convoy left Lerwick
Lerwick is the capital and main port of the Shetland Islands, Scotland, located more than 100 miles off the north coast of mainland Scotland on the east coast of the Shetland Mainland...

 in the Shetland Islands
Shetland Islands
Shetland is a subarctic archipelago of Scotland that lies north and east of mainland Great Britain. The islands lie some to the northeast of Orkney and southeast of the Faroe Islands and form part of the division between the Atlantic Ocean to the west and the North Sea to the east. The total...

—destination of the Norwegian convoys—for the Humber
The Humber is a large tidal estuary on the east coast of Northern England. It is formed at Trent Falls, Faxfleet, by the confluence of the tidal River Ouse and the tidal River Trent. From here to the North Sea, it forms part of the boundary between the East Riding of Yorkshire on the north bank...

. This was to become a regular route. The Norwegian and coastal convoys included airships based out of Scotland (and in the latter case also Yorkshire).

Although the British War Cabinet proposed convoys in March 1917, the Admiralty still refused. It was not until 860334 LT (874,142.4 t) of shipping were lost to U-boats in April that the Admiralty approved convoying all shipments coming through the north and south Atlantic. Rear Admiral Alexander Duff
Alexander Ludovic Duff
Admiral Sir Alexander Ludovic Duff GCB GBE KCVO was a Royal Navy officer who went on to be Commander-in-Chief, China Station.-Naval career:...

—head of the Antisubmarine Division
Anti-submarine warfare
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

—suggested it on 26 April, and the First Sea Lord
First Sea Lord
The First Sea Lord is the professional head of the Royal Navy and the whole Naval Service; it was formerly known as First Naval Lord. He also holds the title of Chief of Naval Staff, and is known by the abbreviations 1SL/CNS...

—Admiral John Jellicoe—approved it the next day. Escorts were to be composed of obsolete cruiser
A cruiser is a type of warship. The term has been in use for several hundreds of years, and has had different meanings throughout this period...

s, armed merchant cruisers and pre-dreadnought battleships for the oceanic portion of the routes, while in the more dangerous waters around Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 they were composed of destroyers. Observation balloon
Observation balloon
Observation balloons are balloons that are employed as aerial platforms for intelligence gathering and artillery spotting. Their use began during the French Revolutionary Wars, reaching their zenith during World War I, and they continue in limited use today....

s—especially kytoon
A kytoon is a kite with a significant amount of aerostatic lift from a lighter than air gas carried within.The primary advantage of a kytoon is that it remains up and at a reasonably stable position above the tether point, irrespective of the wind.The kytoon has been used in peace and war...

s—were used to help spot submarines beneath the surface, the aircraft carrier
Aircraft carrier
An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...

 being then undeveloped. During discussions in March, it was determined that 75 destroyers were needed, but only 43 were available. The first experimental convoy of merchant vessels left Gibraltar
Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...

 on 10 May 1917 and arrived at the Downs
The Downs
The Downs are a roadstead or area of sea in the southern North Sea near the English Channel off the east Kent coast, between the North and the South Foreland in southern England. In 1639 the Battle of the Downs took place here, when the Dutch navy destroyed a Spanish fleet which had sought refuge...

 on 22 May, having been accompanied by the last leg of its journey by a flying boat from the Scillies.


The first transatlantic convoy left Hampton Roads
Hampton Roads
Hampton Roads is the name for both a body of water and the Norfolk–Virginia Beach metropolitan area which surrounds it in southeastern Virginia, United States...

 on 24 May escorted by the armored cruiser
Armored cruiser
The armored cruiser was a type of warship of the late 19th and early 20th centuries. Like other types of cruiser, the armored cruiser was a long-range, independent warship, capable of defeating any ship apart from a battleship, and fast enough to outrun any battleships it encountered.The first...

 , met up with eight destroyers from Devonport
Devonport, Devon
Devonport, formerly named Plymouth Dock or just Dock, is a district of Plymouth in the English county of Devon, although it was, at one time, the more important settlement. It became a county borough in 1889...

 on 6 June, and brought all its ships save one stragglered that was torpedoed to their respective ports by 10 June. The first regular convoy left Hampton Roads on 15 June, the next left Sydney, Nova Scotia
Sydney, Nova Scotia
Sydney is a Canadian urban community in the province of Nova Scotia. It is situated on the east coast of Cape Breton Island and is administratively part of the Cape Breton Regional Municipality....

 on 22 June, and another left New York
Port of New York and New Jersey
The Port of New York and New Jersey comprises the waterways in the estuary of the New York-Newark metropolitan area with a port district encompassing an approximate area within a radius of the Statue of Liberty National Monument...

 for the first time on 6 July. The Sydney convoy had to be diverted to Halifax during winter months. The first regular convoy from the south Atlantic commenced on 31 July. Fast convoys embarked from Sierra Leone
Sierra Leone
Sierra Leone , officially the Republic of Sierra Leone, is a country in West Africa. It is bordered by Guinea to the north and east, Liberia to the southeast, and the Atlantic Ocean to the west and southwest. Sierra Leone covers a total area of and has an estimated population between 5.4 and 6.4...

—a British protectorate—while slow ones left from Dakar
Dakar is the capital city and largest city of Senegal. It is located on the Cap-Vert Peninsula on the Atlantic coast and is the westernmost city on the African mainland...

 in French West Africa
French West Africa
French West Africa was a federation of eight French colonial territories in Africa: Mauritania, Senegal, French Sudan , French Guinea , Côte d'Ivoire , Upper Volta , Dahomey and Niger...

. Gibraltar convoys became regular starting on 26 July.

Confidence in the convoy system grew rapidly in the summer of 1917, especially as it was realised that the ratio of merchant vessels to warship could be higher than previously thought. While the first convoys comprised 12 ships, by June they contained 20, which was increased to 26 in September and 36 in October. The U.S. Navy′s liaison to Britain—Rear Admiral William Sims
William Sims
William Sowden Sims was an admiral in the United States Navy who sought during the late 19th and early 20th centuries to modernize the Navy. During World War I he commanded all United States naval forces operating in Europe...

—and its ambassador—Walter H. Page—were both strong supporters of convoying and opponents of Germany′s unrestricted submarine warfare. Shortly after the U.S. entered the war, Sims brought over 30 destroyers to the waters around Britain to make up the Royal Navy′s deficit.

The success of the convoys forced the German U-boats in the Atlantic
Atlantic U-boat Campaign (World War I)
The Atlantic U-boat Campaign of World War I was the naval campaign fought by German U-boats in Atlantic waters, that is, the seas around the British Isles, the North Sea, and the coast of France. Initially directed against the British Grand Fleet, later it was extended to include action against...

 to divert their attention from inbound shipping to outbound. In response, the first outbound convoy left for Hampton Roads on 11 August 1917. It was followed by matching outbound convoys for each regular route. These were escorted by destroyers as they left Britain and were taken over by the typical cruiser fotillas as they entered the open ocean.

The Germans again responded by changing strategy and concentrating on the Mediterranean theater
Mediterranean U-boat Campaign (World War I)
The Mediterranean U-boat Campaign in the Mediterranean Sea was fought by Austria-Hungary and German Empire against the Allies during World War I...

, where the extremely limited use of convoys had been approved at the Corfu Conference (28 April–1 May 1916). The Mediterranean proved a more difficult zone for convoying than the Atlantic, because its routes were more complex and the entire sea was considered a danger zone (like British home waters). There the escorts were not provided only by Britain. The French Navy, U.S. Navy, Imperial Japanese Navy, Regia Marina (Royal Italian Navy) and Brazilian Navy
Brazilian Navy
The Brazilian Navy is a branch of the Brazilian Armed Forces responsible for conducting naval operations. It is the largest navy in Latin America...

 all contributed. The first routes to receive convoy protection were the coal route from Egypt
Sultanate of Egypt
The Sultanate of Egypt is the name of the short-lived protectorate that the United Kingdom imposed over Egypt between 1914 and 1922.-History:...

 to Italy via Bizerte
Bizerte or Benzert , is the capital city of Bizerte Governorate in Tunisia and the northernmost city in Africa. It has a population of 230,879 .-History:...

, French Tunisia, and that between southern metropolitan France and French Algeria
French Algeria
French Algeria lasted from 1830 to 1962, under a variety of governmental systems. From 1848 until independence, the whole Mediterranean region of Algeria was administered as an integral part of France, much like Corsica and Réunion are to this day. The vast arid interior of Algeria, like the rest...

. The U.S. took responsibility for the ingoing routes to Gibraltar
Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...

, and increasingly for most of the eastern Mediterranean. The commander-in-chief of the Royal Navy in the Mediterranean, Somerset Calthorpe, began introducing the convoy system for the route from Port Said
Port Said
Port Said is a city that lies in north east Egypt extending about 30 km along the coast of the Mediterranean Sea, north of the Suez Canal, with an approximate population of 603,787...

 to Britain in mid-October 1917. Calthorpe remained short of escorts and was unable to cover all Mediterranean trade, but his request to divert warships from convoy duty to the less effective Otranto Barrage
Otranto Barrage
The Otranto Barrage was an Allied naval blockade of the Otranto Straits between Brindisi in Italy and Corfu on the Albanian side of the Adriatic Sea in World War I. The blockade was intended to prevent the Austro-Hungarian Navy from escaping into the Mediterranean and threatening Allied operations...

 was denied by the Admiralty.

With the gradual success of the Mediterranean convoys, the Germans began to concentrate on attacking shipping in Britains coastal waters, as convoyed vessels dispersed to their individual ports. Coastal convoy routes were only added gradually due to the limited availability of escorts, but by the end of the war almost all sea traffic in the war zones was convoyed. The coastal convoys relied heavily on air support. After June 1918, almost all convoys were escorted in part by land-based airplanes and airships, as well as sea planes. The organisation of these convoys had also been delegated by the Admiralty to local commanders.

Admiralty resistance and objections

The main objection of the Admiralty to providing escorts for merchant shipping (as opposed to troop transits) was that it did not have sufficient forces. In large part, this was based on miscalculation. The Admiralty's estimates of the number of vessels requiring escort and the number of escorts required per convoy—it mastakenly assumed a 1:1 ratio between escorts and merchant vessels—were both wrong. The former error was exposed by Commander R. G. H. Henderson of the Antisubmarine Division and Norman Leslie
Norman Leslie, 19th Earl of Rothes
Colonel Norman Evelyn Leslie, 19th Earl of Rothes , a Scottish representative peer, was the son of Martin Leslie Leslie and Georgina Frances Study....

 of the Ministry of Shipping, who showed that the Admiralty was relying on customs statistics that counted each arrival and departure, concluding that 2,400 vessels a week, translating into 300 ships a day, required an escort. In fact, there were only 140 ships per week, or 20 per day, on transoceanic voyages. But the manageability of the task was not the Admiralty′s only objection.

It alleged that convoy presented larger and easier targets to U-boats, and harder object to defend by the Navy, raising the danger of the submarine threat rather than lowering it. It cited the difficulty of coordinating a rendezvous, which would lead to vulnerability while the merchant ships were in the process of assembling, and a greater risk of mine
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...

s. The Admiralty also showed a distrust of the merchant skippers: they could not manoeuvre in company, especially considering that the ships would have various top speeds, nor could they be expected to keep station. At a conference in February 1917, some merchant captains raised the same concerns. Finally, the Admiralty suggested that a large number of merchantmen arriving simultaneously would be too much tonnage for the ports to handle, but this, too, was based in part on the miscalculation.

In light of the cult of the offensive
Cult of the offensive
Cult of the offensive refers to a strategic military dilemma, where leaders believe that offensive advantages are so great that a defending force would have no hope of repelling the attack; consequently, all states choose to attack...

, the convoy was also dismissed a "defensive". In fact, it reduced the number of available targets for U-boats, forcing them to attack well-defended positions and usually giving them only a single chance, since the escorting warships would respond with a counterattack. It also "narrowed to the least possible limts [the area in which the submarine is to be hunted]", according to the Anti-Submarine Report of the Royal Navy Air Service (RNAS) of December 1917. In that month, the First Lord of the Admiralty—Eric Campbell Geddes
Eric Campbell Geddes
Sir Eric Campbell-Geddes GCB, GBE, PC was a British businessman and Conservative politician. He served as First Lord of the Admiralty between 1917 and 1919 and as the first Minister of Transport between 1919 and 1921....

—removed Admiral Jellicoe from his post of First Sea Lord
First Sea Lord
The First Sea Lord is the professional head of the Royal Navy and the whole Naval Service; it was formerly known as First Naval Lord. He also holds the title of Chief of Naval Staff, and is known by the abbreviations 1SL/CNS...

 because of the latter′s opposition to the convoy system, which Prime Minister David Lloyd George
David Lloyd George
David Lloyd George, 1st Earl Lloyd-George of Dwyfor OM, PC was a British Liberal politician and statesman...

 had appointed Geddes to implement.

Types of convoy

According to John Abbatiello, there were four categories of convoy used during World War I. The first category consists of the short-distance convoys, such as those between Britain and its European allies, and between Britain and neutral countries. The commercial convoys between England and the Netherlands or Norway are examples, as are the coal convoys between England and France. The second category consists of the escorts of warships, usually troopships, such as those from the Dominions in the early stages of the war. These formed the earliest convoys, but "probably the most overlooked category". The British Grand Fleet itself could be included in this category, since it was always escorted by a destroyer screen in the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

 and frequently by long-range Coastal
Coastal class blimp
The Coastal Class were a class of blimp used by the Royal Naval Air Service during World War I. The C class blimp operated by the United States Navy after the war was a completely unrelated design. In total 35 Coastals were built, all at RNAS Kingsnorth, Kent...

 and North Sea-class airships
NS class blimp
The British NS class blimps were the largest and last in a succession of non-rigid airship designs that served with the Royal Naval Air Service during World War I; developed from experiences gained with earlier classes to operate off the east coast of Britain on long-range patrols...

. The third category is the so-called "ocean convoys" that safeguarded transoceanic commerce. They traversed the Atlantic from the U.S. or Canada in the north, or from British or French colonial Africa or Gibraltar in the south. The fourth category is the "coastal convoys", those protecting trade and ship movements along the coast of Britain and within British home waters. Most coastal and internal sea traffic was not convoyed until mid-1918. These convoys involved the heavy use of aircraft.

Structure of command

With the success of the convoy system, the Royal Navy created a new Convoy Section and a Mercantile Movements Division at the Admiralty to work with the Ministry of Shipping
Minister of Shipping
The Minister of Shipping was a British government post created during the First World War and again during the Second World War. In 1941 it was merged into the position of Minister of Transport which was then renamed Minister of War Transport....

 and the Naval Intelligence Division
Naval Intelligence Division
The Naval Intelligence Division was the intelligence arm of the British Admiralty before the establishment of a unified Defence Staff in 1965. It dealt with matters concerning British naval plans, with the collection of naval intelligence...

 to organise convoys, routings and schedules. Before this, the Norwegian convoys, coal convoys and Beef Trip convoys had often been arranged by local commanders. The Admiralty arranged the rendezvous, decided which ships would be escorted and in what order they would sail, but it left the composition of the escort itself to the Commander-in-Chief, Plymouth
Commander-in-Chief, Plymouth
The Commander-in-Chief, Plymouth was a senior commander of the Royal Navy for hundreds of years. Plymouth Command was a name given to the units, establishments, and staff operating under the admiral's command. In the nineteenth century the holder of the office was known as Commander-in-Chief,...

. The wing captain of the Southwest Air Group also received notification of the Admiralty′s convoys, and provided air cover as they approached their ports. The Enemy Submarine and Direction Finding Section and the code-breakers of Room 40
Room 40
In the history of Cryptanalysis, Room 40 was the section in the Admiralty most identified with the British cryptoanalysis effort during the First World War.Room 40 was formed in October 1914, shortly after the start of the war...

 cooperated to give the convoy planners knowledge U-boat movements.

With the advent of coastal convoys, escort composition and technique fell into the hands of the district commanders-in-chief.

Use of aircraft

In April 1918, the airship NS-3 escorted a convoy for 55 hours, including patrols at night both with and without moonlight. In complete darkness the airship had to stay behind the ships and follow their stern lights. The only value in such patrols was in maximising useful daylight hours by having the airships already aloft at dawn. In July, the Antisubmarine Division and the Air Department
Air Department
The Air Department of the British Admiralty was established prior to World War I by Winston Churchill. Its function was to foster naval aviation developments and later to oversee the Royal Naval Air Service . Its first director was Captain Murray Sueter...

 of the Admiralty considered and rejected the use of searchlights during night, believing the airships would render themselves vulnerable to surfaced U-boats. Testing of searchlights on aircraft revealed that the bomb payload needed to be much reduced to accommodate searchlight systems. Parachute flares offered better illumination (and were less illuminating of the arships′ positions), but they weighed in at 80 pounds each, making them too costly to drop unless the rough position of the enemy was already known. The Admiralty restricted the use of lights on ariships for recognition, emergencies and under orders from senior naval officers only.

On 26 December 1917, as an airship was escorting three merchantmen out of Falmouth
Falmouth, Cornwall
Falmouth is a town, civil parish and port on the River Fal on the south coast of Cornwall, England, United Kingdom. It has a total resident population of 21,635.Falmouth is the terminus of the A39, which begins some 200 miles away in Bath, Somerset....

for their rendezvous with a convoy, they were attacked three times in the space of 90 minutes, torpedoing and sinking two of the vessels and narrowling missing the third before escaping. The airship had been 7 mi (6.1 nmi; 11.3 km) away at the time of the incident, which was one of the last of its kind. In 1918, U-boats attacked convoys escorted by both surface ships and aircraft only six times, sinking three ships in total out of thousands. Because of the decentralised nature of the convoy system, the RNAS had no say in the composition or use of air escorts. The northeast of England led the way in the use of aircraft for short- and long-range escort duty, but shore-based aerial "hunting patrols" were widely considered a superior use of air resources. Subsequent historians have not agreed, although they have tended to overstress the actual use made of aircraft in convoy escort duty. An Admiralty staff study in 1957 concluded that the convoy was the best defence against enemy attacks on shipping, and dimissed shore-based patrols while commending the use of air support in convoying.
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