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Anti-Submarine Warfare in "Why We Fight"
In my review of "Why We Fight" I expressed some annoyance at the basic premise for the plot of the episode. Here in brief lie the reasons for that annoyance
The Naming of Submarines
The first thing that irked me about the episode was a tiny detail – the reference to the German U-Boat as being of the “T” class. There was in fact a British “T” class of submarine. It was called that because all the boats had names beginning with “T” like HMS Triton or HMS Truncheon. German submarines were not named. They were given numbers i.e. U-531(ie Unterseeboot with hull number 531). As technology and design improved the characteristics of the boats changed and so they were grouped together in Types. So the Type I boat was the first ocean-going class and exhibited poor stability, slow dive rate, poor manoeuvrability under water, and mechanical unreliability. Each succeeding class delivered better performance. The Type VII and the Type IX were the mainstay of the German effort in the battle of the Atlantic. But this is where I come to my main complaint.
The Happy Time
The German success against shipping the the early years had nothing to do with technology. U-boats of the period were not that technologically advanced. They had a good range, carried a good gun and had an adequate number of torpedoes and had good communications (in the form of the enigma code). But they also had weaknesses. First they were slow. On the surface using diesel engines they could maintain a respectable 18-20 knots (still significantly slower than escorts) but underwater they could not use those engines because of the oxygen they consumed so they had to use batteries and were reduced to about walking pace. Their torpedoes in the early years at least were unguided and had to be aimed ahead of the target ship to allow for travel time as well as the effects of currents etc. This reduced their accuracy, especially against ships that were manoeuvering to avoid torpedoes ("zig-zagging"). What gave the Germans their “happy time” was a combination of smart tactics and Allied weaknesses.
Until the fall of France the range of the U-boats had been constrained geographically; access to the Atlantic convoy routes necessitating long and risky journeys from the northern German ports around the north of Scotland. With the acquisition in June 1940, however, of the French Atlantic ports of Brest, Lorient, Saint-Nazaire, La Pallice and La Rochelle the U-Boat commander Admiral Dönitz could take advantage of increased dockyard capacity and proximity to the convoy lanes, which enabled him to extend operations into the central and western Atlantic. Previously arbitrary and sporadic U-boat actions were transformed into more regular and consistent attacks on convoys.
It also allowed attacks in the middle of the Atlantic well out of range of air cover.
To counter the protection provided by travelling in convoy Dönitz had, in the inter-war period, developed 'wolfpack' tactics, whereby packs of submarines co-ordinated and guided by radio would be deployed on the surface at night. Operating on the surface enabled the U-boats to match and exceed the speeds of the merchant ships and overwhelm their escorts.
The Asdic submarine detecting device was useless against vessels on the surface and the low silhouettes of the U-boats were virtually invisible under the cover of darkness. These tactics were based on those used successfully in the latter months of 1918, and it was publicly stated by the Germans before the Second World War that it would be their intention to operate the U-boats in surfaced night attacks. Allied intelligence however apparently missed this.
Dönitz also refined the tactics following problems implementing pack-type attacks in the first few months of the war. Pack attacks against convoys sailing to the UK were best carried out, he concluded, as far out in the Atlantic as possible to give the U-boats several days to press home repeated attacks. Secondly, U-boats making contact with convoys were instructed not attack immediately but shadow the convoy and call up other boats. When the pack had assembled they should attack simultaneously in one massive blow, overwhelming escorts and scattering the convoy.
At the start of the war there had been an acute shortage of escort vessels, a shortage compounded in the Atlantic theatre by the withdrawal of ships to assist in the Dunkirk evacuations, during which many were lost and damaged. Many others had been lost or damaged in the Norway campaign, had been sent to the Mediterranean or retained as protection against the threatened invasion of Britain. This large-scale withdrawal of the convoy surface and air escorts had, as a consequence, "denuded merchant shipping of any effective scale of defence and given the U-boats almost a free hand."
The parlous state of the Royal Navy's convoy escort skills and capabilities at the outbreak of the war are well described in the following passage :
Reversal of Fortunes
Eight things helped the Allies to stop the U-boat menace.
1. The work of the British code breakers at Bletchley Park in deciphering the German Enigma code was vital in giving the Allied navies the edge in the Battle of the Atlantic. In February 1942, however, the German code was improved, resulting in ‘the Drumbeat crisis’ when shipping losses were their greatest – until March 1943, when the German code was again broken. 2. Sonar had been invented before World War I, but after 1942 the US Navy Department developed ‘console sonar’ which could plot accurate bearings using an echo ‘ping’. Training of sonar operators was also improved. 3. Radar was introduced on board all escort vessels and improved so that U-boats could even be detected in bad weather. This curtailed the possibility of surface attacks and reduced submarines to underwater attacks where their lack of speed was a real handicap. 4. The British developed HF/DF (‘huff-duff’), whereby U-boats’ positions could be worked out from their radio transmissions. 5. Longer range aircraft such as B-24 Liberators and Sunderland Flying boats were introduced and six aircraft carriers were sent to patrol the Atlantic, and this extended air cover to the whole route convoys took. 6. Air depth-bombs were developed so that planes could attack U-boats under the water. 7. Weapons called Hedgehog and Squid were developed which allowed attack ships to catapult depth-charges up to 300 yards in front of the ship. 8. The Allies set up hunter-killer groups of ships, including one aircraft carrier with a number of destroyer escorts, to hunt down and sink U-boats.
The turning point was slow Convoy ONS–5 (April–May 1943), when a convoy of 43 merchantmen escorted by 2 destroyers and a frigate was attacked by a wolf-pack of 30 U-boats. Although 13 merchant ships were sunk, the U-Boats were detected by HF/DF, six U-boats were sunk by escorts or Allied aircraft and – despite a storm which scattered the convoy – the merchantmen reached the protection of land-based air cover causing Dönitz to call off the attack.
It was the end of the U-Boat menace – 37 U-Boats were lost in May 1943, and 34 in July. The RAF was able to intercept and sink many U-boats as they left harbour. The Nazis gave their U-boats better anti-aircraft guns, and invented a device called Snorkel (which allowed U-Boats to refresh their air without surfacing). They also introduced "accoustic" torpedoes which would automatically make for the sound of a ship's propellers. "Bottoming" tactics allowed U-boats to avoid detection from sonar and radar. However, after May 1943, the U-boats were on the defensive, and Allied shipping losses fell significantly.
So, the idea of a captured German submarine disclosing all it's war winning secrets is just too fanciful for words.
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