The tide turns
The last major crisis of the Atlantic campaign came in April-May 1943 when, in a series of hard-fought convoy battles, 27 U-boats were sunk for the loss of only 24 merchant ships. More escort ships, better air cover and new tactics and equipment had given the Allies the decisive advantage. Accurate naval intelligence, based on the further breaking of the U-boats’ ‘Enigma’ radio code, also proved vital.
At the end of May all U-boats were withdrawn from the North Atlantic for 6 months. U-boat Command had decided to regroup and concentrate on developing new U-boats and new weapons. Although still a menace to Allied shipping until the very last day of the war, the U-boats were never to regain the upper hand of the Atlantic.
The escorts grow stronger
From mid-1942, more British, Canadian and American naval escorts became available. Some 150 corvettes were in service, new sloops and frigates were beginning to appear, and convoys usually had a close escort of some six ships. On the other hand, many Atlantic escorts were diverted during the year to support the Arctic convoys and the Allied landings in North Africa.
The escorts themselves were often much better equipped than their predecessors. High Frequency Direction Finding (HF/DF or ‘Huffduff’) was now widely in use and with radar and improved Asdic equipment they were much better able to detect U-boats. New weapons, such as the ahead-throwing ‘Hedgehog’ and ‘Squid’ mortars were also introduced, adding greatly to their firepower.
Radar: the battle-winner?
By 1943 many escort ships and aircraft operating against U-boats in the Atlantic were fitted with highly accurate radar (radio direction and range) equipment. Radar, originally known as RDF (radio direction finding) was used above the surface, as Asdic was used below it. A radio wave was sent out, which bounced back when it hit any metallic object. This gave information about the direction and range of the object.
When the war began radar sets were too bulky and inaccurate for use on aircraft or small warships. This was because of the long wavelengths used. By 1941, however, British scientists had developed small radar sets capable of sending waves of ten centimetres and shorter. These could pinpoint a target with remarkable accuracy over great distances. ‘Centimetric’ radar, carried by warships and aircraft, proved to be a crucial, battle-winning device in the Atlantic, as in other theatres of war.
Asdic Type 147 depth recorder
By 1943, the range and accuracy of British Asdic or sonar equipment for detecting submarines underwater had been greatly improved. The Type 147 set was the first to include a depth recorder. With this, the range, bearing and depth of a submarine could often be found. When linked automatically with the new-forward-throwing ‘Squid’ mortar, this set was a major success in the war against the U-boats.
Flags of many nations
While most of the naval escort work during the Atlantic Battle was done by the Royal Navy, the ships of several other navies were also involved. In the last three years of the war, for example, the Royal Canadian Navy carried a burden equal to that of the Royal Navy in convoy protection, and performed admirably. Escorts manned by other countries like Norway, Holland, Poland, Free France, Belgium, Greece and the United States also played their part.
Victory to the escorts
In late April-early May 1943 the escorts of convoy ONS 5 won a decisive victory over the Wolf Packs. For eight days and nights the British B7 Escort Group, led by Commander Peter Gretton (on the destroyer ‘Duncan’) assisted by two British Support Groups, beat off attacks by 40 U-boats, sinking five and damaging many others for the loss of 12 merchant ships. Two other U-boats were sunk by Royal Canadian Air Force and RAF aircraft. Even for the largest U-boat packs, the cost of attacking convoys had become too high. This defeat marked the end of the U-boats’ ascendancy in the Atlantic.
Death from the air
By early 1943 Atlantic convoys benefitted from better air cover. Some were joined by escort carriers for the whole Atlantic voyage. Even more crucially, US Air Force Liberator bombers flying from Iceland and Newfoundland closed the mid-Atlantic ‘Air Gap’ by late April. At the same time more long-range British and US aircraft were made available to attack U-boats in the Bay of Biscay, near their French bases. Equipped with the powerful ‘Leigh Light’ (searchlight) for operations at night, air-to-surface radar, and increasingly effective weapons, these aircraft enjoyed many successes.
The fitting of the highly-accurate centimetric radar to long-range aircraft was a major turning-point in the anti-U-boat campaign. More U-boats were sunk by Aircraft than by Ships during the last two years of war.
RAF Coastal Command
RAF Coastal Command played a decisive role in the Battle of the Atlantic, particularly from 1943 onwards. In all, it sank at least 155 U-boats in Atlantic waters for the loss of 646 aircraft (all causes)
RAF Coastal Command was a multi-national air force. As well as RAF and Royal Naval squadrons, units of the Royal Australian Air Force, Royal Canadian Air Force, Czech and Polish Air Forces, the US Navy and US Army Air Force were attached to Coastal Command for Atlantic operations.
'A hunting we will go'
Captain FJ (‘Johnny’) Walker, CB, DSO and three Bars, was the most famous escort commander to be based at Liverpool during the war. Walker, a specialist in anti-submarine warfare was an unorthodox and inspirational officer who won great respect and affection from his men. Following his unrivalled success in command of the sloop ‘HMS Stork’ and the 36th Escort Group, in early 1943 he was put in command of ‘HMS Starling’ and five other sloops of the Second Support Group. His brief was to spearhead the escorts’ offensive along the northern convoy routes by attacking and sinking U-boats at every opportunity. This he did brilliantly, soon becoming widely known as the Royal Navy’s prime ‘U-boat killer’. At Walker’s insistence, the Group’s jaunty them tune ‘A-hunting we will go’ was played over a loudhailer on ‘Starling’s bridge whenever she left harbour.
Between 1 June 1943 and 1 July 1944 the ships of Walker’s Second Support Group sank 15 U-boats. Walker was a great exponent of teamwork, making very successful use of Asdic, HF/DF (high-frequency direction-finding) and inter-ship radio. One of his famous ‘creeping attacks’ lasted over thirty hours before the U-boat concerned was sunk.
Signal flags: 'General Chase'
The ‘general chase’ signal was hoisted by Walker’s order, on the sloop HMS KITE (Starling being under repair) in the Bay of Biscay in July 1943 to order the ships of his group to attack three surfaced U-boats in the area. One of these U-boats were later sunk by a Sunderland Flying Boat of RAF Coastal Command, the other two falling victim to Walker’s group.
The ‘General Chase’ signal had only been used twice before in the Royal Navy – once by Sir Francis Drake, when he chased the Spanish Armada from the Channel in 1588, and again by Nelson when he defeated Napoleon’s fleet at the Battle of the Nile in 1798.
Death of a hero
Exhausted by the demands of war, Walker died of a stroke in July 1944. He was buried at sea in Liverpool Bay after a funeral service with full naval honours at Liverpool Cathedral. But his methods and examples were to have a lasting effect on the Allied anti-submarine campaign. After the war, Admiral Horton, C-in-C Western Approaches, considered that victory in the Atlantic was due more to Walker than to any other individual.
"Victory has been won, and should be won, by such as he." Admiral Sir Max Horton at Walker’s funeral, July 1944.
The convoys get through
1943 was the year in which most of the American and Canadian troops and supplies needed for the invasion of Europe were being sent across the Atlantic. Victory in the Atlantic was the essential prelude to victory in Europe.
'SS Marwarri' 1936
Owned by the Liverpool based Brocklebank Line Ltd, ‘Marwarri’ was requisitioned by the British Government in 1939 and did sterling service throughout the war. Between June and August 1944 she made seven return passages to the Normandy beaches, carrying thousands of troops and vehicles for the invasion of Europe. Her first shipment was of 570 troops and 185 vehicles of the crack 51st Highland Division.
The merchant ships and seamen of Britain and her allies were vital in supporting the Allied invasions of North Africa, Southern Italy and France.
Nowhere to hide
Once the Allies had gained the advantage in the Atlantic campaign, there was no escape for the U-boats. Although the Germans developed new U-boats, weapons and equipment, they came too late. Renewal of the U-boat offensive in the Atlantic was ended by Allied advances in Europe.
"My U-boat men! …You have fought like lions… Unbeaten and unblemished you lay down your arms after an heroic fight without parallel." Grand-Admiral Donitz, 4 May 1945.