by James Jinks
At the end of the war the sonar equipment installed in Royal Navy submarines was primitive and suffered from a number of limitations. In good conditions its bearing accuracy was plus or minus 2 degrees and it took from five to ten minutes to detect an alteration of course by an enemy at a constant speed. The equipment also only worked on a limited frequency. When noise trials had shown that submarine machinery and propellers generated noise over a wide band of sonic and super-sonic frequencies, lower-frequency noises, which could be detected at greater ranges, could not be heard. There was also no method of obtaining the depth of a target. Unless a periscope or snort mast was seen, the noise of diesel engines heard, or the target restricted by shallow water, there was no means of knowing whether an enemy submarine was operating at a depth of 40 or 400 feet. Self-generated noise was also a considerable problem. Royal Navy submarines attempting to remain silent in order to use passive sonar equipment to detect enemy submarines were required to operate at a low speed of around 2 knots, which prejudiced the chances of reaching a good firing position, or obtaining a firing position at all. Quieter submarines were required.
Another early difficulty was that the Submarine Service’s primary torpedo, the Mark 8, was ill suited to anti-submarine warfare. Although the torpedo had been trial-run at depths down to 200 feet, the equipment which set the depth of the torpedo was incapable of allowing a greater depth than 44 feet once the torpedo had been loaded into a torpedo tube. The enemy could also often hear the torpedo approaching and move out of its way. Trials had shown that a Mark 8 torpedo travelling at 45 knots could be detected by an enemy submarine from a range of as much as 1200 yards. In the 48 seconds it took the torpedo to cover that distance, an operator on board an enemy vessel had 15 seconds to classify the noise as a torpedo, 15 seconds to warn the Officer of the Watch and 18 seconds in which to take evasive action, by increasing speed, altering course and changing depth. Trials revealed that even with just 18 seconds’ warning, an ‘A’ class submarine, snorting at 6 knots, could manoeuvre in such a way that less than 30 per cent of it remained in the target area when the torpedo arrived. This reaction time was only likely to improve as more advanced submarines entered service. The Mark 8 torpedo, FOSM concluded, had ‘only a small chance of success against a reasonably alert enemy fitted with acoustic equipment similar to our own, unless the firing range is short, or the depth of water insufficient to permit the target taking evasive action in depth’.114 New torpedoes and fire control systems were also required.
The first serious submarine versus submarine exercises to simulate attacking Soviet submarines operating near their bases were held in June and July 1950 in the waters around Skye, with the islands of Canna, Rum and Eigg acting as the Kola Inlet. HMS Alcide, under the command of Lieutenant Morris ‘Roache’ O’Connor, played the role of the Soviet submarine, while the attacking submarine was played by HMS Truncheon, under the command of Lieutenant A. Richardson. Truncheon was modified by the staff of the depot ship HMS Montclare to reduce the amount of noise that it generated. Noise generated by water flowing over a submarine’s hull, by machinery and cavitation from propellers served to drastically degrade the submarine’s own sonar performance. It also served to betray its position to a potential enemy. As with Tradewind, Truncheon’s 4-inch gun and external bow torpedo tubes were removed to streamline the hull and reduce the noise of water flowing around the hull. The submarine was also equipped with an American hydrophone as well as equipment that allowed the CO to monitor the amount of noise his submarine was making.
Although these modifications allowed Truncheon to manoeuvre silently close to its target and into an attacking position, Truncheon only claimed eleven successful attacks out of thirty-two. Neither submarine could remain silent at speeds above 3 knots and Alcide succeeded in attacking Truncheon on six occasions while the submarine was noisily snorting. The final stage of the exercise consisted of a five-day patrol in the Minches. Truncheon was allocated a patrol area of forty square miles and was ordered to hunt HMS Alcide, representing an enemy submarine on passage to and from patrol and her base. Over the course of five days and nights, Alcide conducted eighteen runs through the area, eleven while snorting, three on the surface, and four dived. Truncheon, which had no forewarning, detected twelve of Alcide’s runs and carried out ten attacks, four of which were judged to be successful. The remaining six undetected intrusions were explained away by adverse weather, which deteriorated water conditions.115
The results of the exercise were disappointing. Further intensive studies led the new Flag Officer Submarines, Rear Admiral Guy Grantham, to conclude that ‘a submarine fitted with present equipment stands a good chance of achieving some detections of the enemy, but due to other aspects of the problem, the chances of a successful attack cannot be considered as very high’.116 Inaccurate sonar equipment imposed ‘limitations on the accuracy of the torpedo fire control data’ and (as we have seen) there was still ‘no method of obtaining the enemy’s depth’.117 Grantham had also concluded that one of the biggest problems was that ‘the present general-purpose submarine, with its gun and other projections, all of which reduced its efficiency as a silent listening platform is, for this reason, unlikely to be very successful in its A/S role’.118 In 1958 one officer on FOSM’s staff summed up the state of affairs: ‘we are armed with World War II equipment. Our asdic is a short range passive detector; our torpedo is a non-homing straight runner, and we are therefore unable to fire at anything below periscope depth.’119
The Service concluded that its future submarines had to be equipped with high-performance sonar, specifically designed for anti-submarine warfare, as well as a torpedo armament capable of homing in on enemy submarines. Prolonged submergence became the priority, especially as submarines were required to carry out their traditional task of patrolling in enemy-controlled waters. Tactically, high, silent speeds were also important to increase the chances of detecting, intercepting and ultimately attacking submerged targets. This represented a significant shift in thinking. The emphasis moved away from the high-speed, low-endurance submarines, such as offered by HTP propulsion, towards moderately low-speed, high-endurance and silent submarines.
To meet these new requirements the Navy embarked on an ambitious programme to modernize many of its wartime submarines. At the end of the Second World War a number of the ‘S’ class had also been streamlined and converted to act as fast targets in anti-submarine warfare exercises. These experimental craft, along with the lessons learned from captured German Type XXI submarines, led to major modernizations of the ‘T’ class. HMS Taciturn, the first of the class to undergo such improvements, was fitted with an additional 14 feet of pressure hull to accommodate an extra battery section and an additional pair of motors. Her hull form was streamlined in a manner suitable for high submerged speeds, while the gun and external torpedo tubes were removed from the casing, giving the bows a cleaner line. The fin, which encased seven masts, was also streamlined and the bridge replaced with a modified conning tower. These modifications enabled the ‘T’ class submarines to remain continuously submerged at periscope depth, dive to greater depths and close a higher percentage of targets to effective torpedo range while submerged with a maximum underwater speed of about 17 knots.
Between 1948 and 1957 eight of the welded ‘T’ class were modified in a similar way, but with slight differences, progressive modifications that contributed to the boats’ nickname of ‘T Confusions’ but their underwater performance was transformed. They were also known as ‘T-Conversions.’ It was also decided to streamline five of the riveted ‘T’ class boats and fit a higher-capacity battery without lengthening them. They were known as ‘Streamlined T-boats’ or ‘Slippery Ts’. The work was carried out in the normal refit cycle. It increased underwater endurance by 30–40 miles and their speed at periscope depth was increased by 1.4 knots and maximum quiet speed by almost a knot. They could go faster than the unmodified boats and make less noise while doing so.
New
equipment, as Captain Arthur Hezlet explained in a 1954 presentation on ‘The Future of the Submarine’, also promised to transform the capabilities of the service and the ability of its submarines to meet their new primary wartime role:
Firstly we should hear the enemy at double the range and so make many more contacts; secondly we should be able to listen for longer periods and snort for shorter periods and so have a greater ‘patrol efficiency’. Thirdly we should be able to follow up the contacts at higher speed without being heard and should have improved weapons and their fire control which will at least double the chances of hitting. Within a few years then, we hope the results already being obtained in exercises will be greatly increased.120
This was optimistic. Development of new sonars, fire control equipment and torpedoes was plagued with difficulties. The Submarine Service’s standard wartime sonar set, the 129/138 combination was upgraded and renamed the Type 169/168. A sophisticated new sonar, known as the Type 171, or ‘Four Square’, was intended to provide submarines with a three-dimensional underwater picture. However, it was cancelled in the early 1950s after early trials revealed its performance was unsatisfactory unless used in combination with powerful computers, which could not be accommodated inside contemporary submarines.121 The Naval Staff struggled to envisage a clear role for the new set and decided that its only useful function was the ability to detect mines.122 Instead, a new form of sonar known as the Type 187, a medium-range passive directional-listening set that was housed in a distinctive enclosed dome on the front of the submarine, was eventually introduced in the streamlined ‘T’ class towards the end of the 1950s, alongside a fin-mounted aft-looking hydrophone known as the Type 719.123 These sets only offered a modest improvement in capability. The ability to detect other submarines remained short, especially when compared to what was to come in the future. The official historian of Britain’s sonar programme argued that the many ‘false starts’ in the immediate post-war period were ‘because the Naval Staff found it difficult to formulate requirements’.124
New fire control equipment that was capable of handling the uncertainties of bearings and range when attacking submerged submarines was also needed. It was possible to determine a fire control solution using what limited sonar information was available, but this rarely worked in practice. The Navy’s submarines were equipped with primitive, rudimentary torpedo fire control systems and attacks depended on the considerable skills of the Commanding Officer, who had to ensure that the submarine was pointing ahead of a target. He would then repeatedly check the target’s range and bearing by looking through the periscope while his observations were entered into an electrically driven mechanical fire control computer known as the ‘fruit machine’. While effective, the ‘fruit machine’ was limited and its accuracy was only as good as a CO’s visual observations. A more advanced fire control system known as Torpedo Control System (Submarines) Mk 3 (TCS(S)3) was meant to be capable of taking information from sonar, radar and periscope observations and setting the running depth and angle of torpedoes. Although the first sets appeared in 1955 they were criticized for being complicated to operate.125
Aside from fire control equipment, new torpedoes were also required. The wartime Mark 8 remained the primary submarine weapon in the immediate post-war years. It was repeatedly modified to increase its chances of striking submerged submarines, principally by allowing it to operate at depths of up to 200 feet. Reducing the time it took for a torpedo to reach its target was also seen as a way of increasing the chances of a successful submerged attack. Development work started on a modified Mark 8 capable of high speeds, fuelled by hydrogen peroxide, known as the Mark 12 ‘Fancy’. Advanced acoustic torpedoes that were able to home in on submerged targets also offered a possible solution to the problem of inadequate sonar and fire control equipment. There were two types of homing torpedo. Active homing torpedoes transmitted high-frequency acoustic pulses to detect and intercept a target, while passive homing torpedoes used built-in sonars to home in on a target’s noise signature. Both had disadvantages. Passive homing torpedoes were limited by their own self-noise, slow, only effective against noisy submarines, and susceptible to decoys and other countermeasures. Active homing torpedoes immediately alerted the target to the incoming torpedo, allowing it time to take evasive action either by escaping or by deploying decoys and countermeasures.126 Both the Germans and the Americans developed acoustic torpedoes during the war. The American torpedoes were made available to the Royal Navy, which also started to experiment with another modified Mark 8 equipped with active homing capabilities. The torpedo, which was known as ‘Trumper’, reached the trials stage but was cancelled at the end of the war to save money.127 Instead the Navy refocused its efforts and started work on a battery-powered passive homing torpedo known as the Mark 20(s) ‘Bidder’, which it hoped to use against both submarines and surface escorts.
While this new equipment was being developed, submariners compensated for the inadequacies of their existing equipment and torpedoes in a number of ways. They devised complex choreographed actions from which an attacking submarine could arrive at a fire control solution without using active sonar. This depended on the attacking submarine obtaining the bearings of a target at equal time intervals, first with zero own movement, by pointing straight at the target, followed by another set of bearings, with maximum own movement, which was achieved by altering the attacking submarine through 90 degrees. If the enemy remained on a steady course, its course and speed could be devised by overlaying a rule marked off to the right scale at equal time intervals. A vertical perspex plot on which coordinates of time against true bearings were marked was introduced into submarine Control Rooms. On one side stood a rating with a headset from the sonar operator, marking with a pencil each hard bearing reported. On the other side of the perspex plot an officer faired off all the raw data into a smooth line from which he could then read off for the navigator, who would plot the bearings at predetermined exact intervals. Traditional visual attacks, conducted through the periscope, where the target was visible, would be over in a matter of minutes. These new methods required meticulous detective work as well as patience.128 To compensate for the lack of accurate information about a target’s bearing and range and increase the chances of carrying out a successful attack, submariners fired salvos of Mark 8 torpedoes. Finally, to bring about ‘steady improvement’ in submarine versus submarine operations a submarine versus submarine phase was introduced into FOSM’s annual Summer War Exercise and in 1951 and 1952 the whole of the Summer War was devoted to submarine versus submarine operations.
The service was also hampered by the fact that the rest of the Royal Navy tended to think that the purpose of the submarine fleet was to provide anti-submarine training to its surface and air forces. ‘I think you will agree that the submarine must become perfect in its operational functions of attacking both U-boats and surface targets,’ pleaded Admiral George Simpson, the Flag Officer Submarines from 1952 until 1954.129 He urged the Navy as a whole to ‘think of us as the greatest spearhead – off enemy-controlled ports in enemy-controlled waters – for sinking U-boats in parts of the ocean through which they have got to pass to get to their bases’.130 Exactly when the Submarine Service might be called on to carry out its new role was an uncertain question, but by the early 1950s who the enemy would be was alarmingly plain.
THE EARLY COLD WAR
Immediately after the Second World War the possibility of conflict with the Soviet Union seemed distant and improbable. However, by 1947, East–West relations had deteriorated markedly. In March, President Truman, responding to Soviet-backed communists in the Greek Civil War as well as growing Soviet influence in Turkey, told the US Congress that ‘It must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or outside pressure.’ Two months later, in June 1947, the European Recovery Programme, the so-called Marshall Plan – financial aid to help rebuild European countries – was
rejected by the Soviet Union and its Eastern European allies. In March 1948, a communist coup in Czechoslovakia and ongoing disagreements about the future of Germany led to the first major crisis in the Cold War, when the Soviet Union decided to blockade the land and water routes from the western zones of Germany into the West’s enclaves in Berlin. On 9 July 1948, British ministers and the Chiefs of Staff considered the question: ‘Should we be prepared to go to war over Berlin?’131
Meanwhile, British naval planners, contemplating a future war, operated under a number of assumptions. First, ‘In the foreseeable future there is no maritime power other than Russia with whom we are likely to go to war.’ Second, ‘We will not go to war with Russia unless America is on our side from the outset.’ Third, ‘The size of the fleet which this country will be able to support in the future will be severely restricted by economic factors.’ Fourth, ‘The main task for our Navy in war will be to support what the Chiefs of Staff have stated to be the main pillars of our strategy. From a naval point of view these are the defence of sea communications, the defence of the U.K., and the defence of the Middle East.’132 Prior to the formation of NATO in 1949, the United States Navy and the Royal Navy identified the Barents Sea, the White Sea approaches, and the Danish Straits as key Soviet submarine operating areas that would be defended by Royal Navy and United States Navy submarines. During 1949, the US Joint Chiefs of Staff prepared a plan called ‘Dropshot’ that, although never formally adopted, revealed the outlook of British and American strategists. In the event of war with the Soviet Union, Dropshot foresaw strikes by four US and two Royal Navy aircraft carriers operating in the Barents and Norwegian Seas against enemy submarines and airbases in the Kola Peninsula.133
