All the advances in technology made by the British ensured that U-boats could be detected much earlier than was possible at the start of the war. This allowed appropriate offensive or evasive action to be taken efficiently. Also, the measures to track U-boats allowed the British command to plot their positions throughout the Atlantic. The new technology helped to swing the Battle of the Atlantic in Britain’s favour by making the previously invisible U-boats visible and can be considered as a very significant reason for Britain’s success in the Atlantic.
In addition, new weapons were developed to attack U-boats. One such weapon was the hedgehog mortar. The advantage of the hedgehog over the main anti submarine weapon, the depth charge (a device set to explode a certain depth) was that it could be thrown forward, several hundred feet ahead of the ship. The depth charge had to be released when the ship was directly above the U-boat and at this point ASDIC contact would be lost. However, when the hedgehog was used, ASDIC contact could be maintained during firing. Also, the projectiles launched only exploded upon contact with the U-boat and could not explode at the wrong depth causing disturbances in the water and interfering with ASDIC.
Another major anti-U-boat weapon was aircraft which could bomb or gun a surfaced U-boat or depth charge a submerged one. At the start of the war, there was an area in the mid-Atlantic that was out of the range of aircraft based in either Britain or the USA. The ‘mid-Atlantic gap’ was filled in two ways. One was the development of Very Long Range Aircraft which had the capacity to fly into the air gap. The other was the introduction of escort carriers. These ships carried aircraft which could take off and land on elongated decks. Complete air cover throughout the Atlantic was highly valuable as it meant that the U-boats had no safe areas to lurk in and were constantly under threat. The new weapons helped Britain gain control in the Atlantic as they provided a varied arsenal with which to attack U-boats. However without the advances in tracking technology they would have been useless. The improved weapons and the improved detection capabilities used in tandem provided a very unpleasant prospect for the U-boats.
In order to use the new equipment efficiently, new anti-U-boat tactics were introduced. All senior escort officers were sent to the W.A.T.U. (Western Approaches Tactical Unit) to learn specific anti-U-boat tactics. Each tactic was clearly defined and different tactics used depending on certain factors such as the location of the U-boat and the time of day. The new tactics helped to swing the battle Britain’s way as they provided senior escort officers with efficient ways to hunt down U-boats. Also the better training at the W.A.T.U., which included a simulation of an Atlantic crossing called ‘the game’, allowed the senior escort officers to be able to effectively implement the new improved tactics.
Although ‘the game’ was useful, it was no substitute for actual experience of anti-U-boat warfare. Often the most experienced escort groups were reorganised into ‘hit squads’ whose objective was not to escort convoys but to hunt down U-boats. The success enjoyed by these groups as the battle began to turn Britain’s way was testament to the value of the experience gained by senior escort officers in the early years of war when success against U-boats was not as profound.
Another British tactical change helped them greatly to gain control in the Atlantic. This was the relocation of the Royal Navy command from Plymouth to a new underground facility in Liverpool known as the Western Approaches HQ, the heart of which was the operations room which allowed the coordination of all the data from the Atlantic, such as suspected U-boat positions and weather reports. As well as the command of the ships the Western Approaches HQ also had the command of aircraft at the Royal Navy’s disposal. This was a stark contrast to U-boat command in France which operated out of a commandeered villa and relied on a small number of men. Western Approaches HQ allowed the efficient command of the British Atlantic campaign and was certainly a reason for the success of Britain’s resistance in the Atlantic.
Another significant factor aiding Britain’s Atlantic war effort was the entry of the USA into the war. This made the vast American production capabilities fully available to Britain. The USA began a massive shipbuilding programme and by 1942 merchant ‘liberty ships’ were being produced at a rate of 3 per day. By the end of 1943 some 1500 ships had rolled down the slipway. This, coupled with the major advances in anti-U-boat warfare meant that the German objective, to close the supply route by sinking an unsustainable rate of British vessels in the Atlantic to force the country into submission was almost certainly unachievable.
American participation also allowed the involvement of the US Navy and Air Force. This was of great help to Britain as the Royal Navy now had another major Navy to share escort duties and more aircraft in the Atlantic at any one time; therefore the threat to U-boats was greater. Thus it could be said that the USA’s entry into the war was the most significant factor in helping Britain gain Atlantic superiority. With the USA involved, the battle was moved onto a new scale with U-boats facing two merchant fleets and two navies as opposed to one of each.
At the start of the war, the Enigma cipher that the Kriegsmarine used for communications with U-boats was so complex it was considered virtually unbreakable. However, following the recovery of an Enigma machine from a sinking U-boat, the British were able to begin to read the cipher. By mid 1941, Western Approaches HQ was being provided with Enigma decrypts known as ‘Ultra’. It became apparent to the U-boat commander Karl Dönitz that his codes were not safe and so in late 1941, the cipher was changed from the Dolphin cipher to the more complex Shark cipher causing an ‘Ultra’ blackout for most of 1942. However, by 1943, the Shark cipher had been cracked and could be read with relative ease. The breaking of the Enigma cipher was key in Britain’s success in the Atlantic as it allowed the Admiralty to build up a clear picture of U-boat positions and objectives and use this knowledge to warn shipping.
Also, as Enigma was being broken, Royal Navy codes, which had already been broken by the Germans, were being made more secure. This was another advantage for Britain, as the U-boats could not as readily get important information about convoys.
A change in personnel at the Admiralty also helped the British Atlantic cause. Sir Max Horton was appointed Commander-in-Chief of the Western Approaches in November 1942. He was a former submariner who now sought to protect against submarine attacks thus he was referred to as a ‘poacher turned gamekeeper’. He was tough, determined and ruthless committing himself entirely to the cause and expecting the same from all those under his command. His leadership could be said to be a reason why escort fleets and hit squads began to operate more efficiently.
The increasing British success in the Atlantic owed much to great efforts by Britain and her Allies to crush the U-boats however there were also certain weaknesses which were not dealt with by the Kriegsmarine. Thus, the Germans inadvertently aided the British.
For example, at the start of the war the U-boat fleet consisted of a small number of boats with experienced crews. However, as the number of U-boats grew, the Kriegsmarine was unable to give new crews adequate training forcing inexperienced crews to go on war patrols. Often inexperienced crews could not operate as efficiently. In addition to this, experienced commanders, ‘aces’ such as Günther Prien and the man who sunk more allied shipping than any other, the ‘tonnage king’, Otto Kretschmer were lost or captured. As well as losing valuable commanders and crews this also dented the German morale as the ‘aces’ were seen as heroes.
Another German weakness was the failure to fund sufficiently the development of the type XXI and XXIII U-boats. These were true submarines, with greatly superior underwater capabilities to those of the standard U-boat. Britain had developed the capabilities to deal with a standard U-boat but it is unlikely that they would have been able to deal with a type XXI or XXIII as easily. The standard U-boat was essentially the same as the World War I U-boat; another case of under-development.
Another weakness was the diversion of resources elsewhere. Experienced commanders were asked to retire from active service and take up positions ashore. Many accepted, thus depriving the U-boat fleet of yet more experience. This was in contrast to the British attitude which placed value in experience. Another example can be seen in Dönitz, the commander of the U-boat fleet. In January 1943 he was promoted to Groβadmiral and given command of the whole of the Kriegsmarine. This somewhat diverted his attention and commitment from the U-boat cause. Further weaknesses were the inability to out-produce the allied nations and the inability to counter HF/DF by maintaining radio silence.
In conclusion, no single factor caused Britain to gain the upper hand in the Atlantic by mid-1943. However, many of the contributing factors can be summarised by the notion that the British took a more open-minded approach. They were constantly evaluating, developing and changing every aspect of anti-U-boat warfare, whereas the Germans were reluctant to alter a system which had initially worked so effectively.
There were many contributing technical factors. Often an advance in one area would demand an advance in another. For example, radar demanded better training so that it could be used effectively. This was key as it allowed improvement to be the mother of improvement.
It is difficult to place the technical factors in any order of significance as often one factor was reliant on another. However if there was one factor more significant than any other it could be said to be the entry of the USA into the war as Britain became allied with one of the most rich and powerful nations on earth.