The convoy system is about as old as sea trade itself. Vessels would travel together for mutual support in pirate haunted seas or in times of war.

The value of the convoy system to Britain which relied on sea trade for survival was well learnt, during the wars with France in particular the convoy system was well established and each would normally be protected by RN Sloops and Frigates. So important was the convoys that Nelson went into battle at Trafalgar without most of his Sloops and Frigates as they were left in the Mediterranean to guard vital convoys.

Demand for these small general purpose ships was often torn between the need of the Fleet and the protection of convoys, and this situation did not change when the Destroyer came along to replace them.

A convoy gathers in WWII

Despite the long practise of the convoy the Admiralty made no attempt to instigate the system at the start of WW1, arguing that a convoy would simply represent a large target for modern raiders.

In part this had merit, the speed difference between a merchantman and a warship had become profound. Previously an outgunned escort could be expected to delay an attacker while a convoy scattered for safety, but now it was argued that a modern surface raider would easily catch the fleeing ships one by one. A similar argument was used against the U-Boat, that an attacking boat would simply flood the convoy area with torpedoes to devastating effect.

It was the French who managed to get the convoy system reinstated, to some degree. France relied heavily on imports of British coal and these were being decimated by U-Boat attacks. Pressure was brought to bear and the Admiralty reluctantly organised the collier ships into convoys, with an immediate and measurable improvement in survivability.

Limited convoys were introduced elsewhere and proved their worth, with the advent of unrestricted submarine warfare in 1917 losses rocketed and finaly Atlantic convoys were introduced and were highly succesful.

But the Admiralty was very reluctant to release Destroyers to the task of escort, preferring to keep them as Fleet Units. Older Destroyers were released, but proved less than suitable, designed for high speed operations they did not perform well at slow convoy speeds and lacked adequate range.

SMS Scharnhorst, one of the German cruisers sent to sea at the start of WW1 to raid British shipping around the world. One argument against convoys was raiders like this would find them easy pickings.
HMS Venomous, Destroyers were considered too valuable as Fleet Escorts to be used as Convoy Escorts, and their design did not suit long slow hauls defending a slow moving convoy.

Sloops had been re-introduced during the war, these were cut down Destroyers, slower and less well armed, they were designed to act as Fleet Minesweepers. A number of these were released for convoy escort work and proved very effective, later builds of Sloops omitted the mine sweeping gear in favour of all depth charges and some were designed to resemble merchantmen to lure U-Boats into a surface engagement. History knows these as Q-Ships.

After the war those Sloops kept in service were assigned to roles as colonial gunboats, where they again showed their worth and more were built to replace them. But in defiance of experience these between the war Sloops were again built to have a wartime role as Fleet Minesweepers rather than as Escort Vessels.

Concentrating on conventional gun armaments and relatively high speeds the ships could only by constructed in specialist military yards and with the outbreak of WWII Germany immediatley launched a fierce submarine war against Britain, using their experience gained from WWI. Although this time the convoy system was re-introduced at once this time a severe lack of escorts and the U-Boat tactic of massing into Wolf Packs before attacking meant that convoys began to suffer heavy losses.

Unable to build Sloops in sufficient numbers the RN rushed small merchant built Corvettes into service, then larger Frigates built along similar lines. A dedicated Escort Destroyer, the Hunt Class was introduced, but although it excelled in the hostile air enviroments of the North Sea and Mediterranean they were - like their WWI counterparts - unsuitable for the long slow slog of the Atlantic convoys. Although America and Australia embraced the Escort Destroyer (DDE) concept the RN firmly rid itself of it post war.

With the advent of new and faster submarines, late in the war by the Germans and then adopted and improved on by Soviet Russia post war, the RN believed only an Escort vessel as fast as the new submarines would suffice to defend against them and modified war time destroyers into fast frigates and general purpose Escorts, these latter, although by every definition in fact Destroyer Escorts, were nevertheless also classed as Frigates.

Although virtualy bankrupt there was a critical post war need for a purpose built escort vessel which could be mass produced at need as all war built Escorts were now perceived as obsolete. Alliance, later formalised as NATO, strategy called for a rapid reinforcement across the Atlantic in the event of war with Russia, the convoys would have to be guarded and so would the carrier task forces which would act as hunter killer groups. Although the converted Destroyers provided a stop gap measure they suffered from the same problems Destroyers had in the past: poor range, inefficient and unstable at low speeds, and built for speed they lacked the hull capacity for new technology systems.

Designers then had a seemingly impossible task. They needed a ship with the speed of a Destroyer, which could cruise at low speed, operate in any weather, carry extra equipment and was cheap and easy to build. The DDE concept was attractive since it seemed to promise an all purpose ship, but having faced near defeat twice now to the Submarine the RN was not to be seduced. In the Type 15 and Type 16 they had a comparison between a dedicated ASW ship and the DDE general purpose and the value of the dedicated ship was soon proven in trials and excercises.

HMAS Marguerite, classed as Fleet Minesweepers the WW1 Flower Class Sloops saw extensive service as convoy escorts later in the war once the convoy system was initiated. Typical of the class she carried minimal guns, her Minesweeping gear could be replaced by depth charges and they were able to cruise with a convoy for long distances in all weathers.

Despite the bitter lessons of WW1 the RN on the eve of WWII was without a dedicated anti-submarine Escort Ship. The Flower Class like HMS Betony pictured above were a desperate attempt to remedy that.

HMS Oakley, the Hunt Class Destroyer was an attempt to produce a budget Destroyer that could serve as a convoy escort. The relatively small space given to depth charges compared to guns reflects the reluctance to drastically alter traditional Destroyer armaments. Possibly one reason why the Frigate Class was re-introduced, in order to make a clear distinction between the role of Convoy and Fleet Escort.

As in the previous two wars it was anticiapated the main battleground would be the coasts of Britain, the approaches to the Atlantic and the Atlantic itself. Escort ships would need to protect both the convoys and the Carrier Task Groups that would form the core of hunter killer groups. One hard won lesson was that a convoy was not just a good form of defence, it was also bait, instead of hunting the oceans for illusive submarines a Hunter Killer Group had only to intercept enemy submarines as they sought to catch a convoy.

A number of different types of Escort were anticipated would be needed, mirroring in many ways the ships that had served in WWI and WWII, from small coastal escorts to long range deep ocean escorts and from air defence ships when operating in reach of enemy aircraft to fast submarine killers. Work began on the design of a hull which could be common to as many of these requirements as possible, following the example of the Loch Class which had proved adaptable to the Bay Class anti-aircraft Frigate, a standerdised hull would cut costs immensely and with pre-fabrication ensure the rapid build up of forces even if specialist dockyards were destroyed

HMS Termagant, a T Class Destroyer converted to an Escort Vessel. Armed with guns, torpedoes and Squid depth charge mortars she was technicaly an Escort Destroyer (DDE) but the RN began to classify any ship whose primary role was Escort as a Frigate, later the term would term would change to mean a small Anti Submarine ship