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ANTONY PRESTON, JOHN BATCHELOR
THE SUBMARINE SINCE 1919

German "Milch Cow" Type XIV. To extend the range of the Type VII U-Boats, the German Navy built ten submarine tankers in 1941. With a fatter and shorter hull than the Type IX boats, and less power, they could carry sufficient fuel to keep four or five U-Boats at sea for twice as long as usual, and they also carried four spare torpedoes in external stowage. They were made top priority targets for Allied ships and all ten were sunk. Displacement: 1,688 tons (surfaced). Armament: Two 37-mm AA guns; one 20-mm AA gun; no torpedo-tubes

Galling though these losses were, the British and Americans were able to coordinate their counter-measures very well. The programme of 50 British destroyer escorts (BDEs) was hurriedly expanded to 250, and further designs were put into mass-production, so that eventually over 1,000 hulls were on order by 1943. As an emergency measure, Lend-Lease was put into reverse to allow 25 "Flower" Class corvettes to be transferred to the USN, and the new British escort design, the "River" Class frigate was put into production in American yards. But convoy proved to be the essential measure once again, and when introduced brought the shipping losses back under control.

Not that the position of the Allies was anything but alarming. In 1941 Great Britain had lost a total of 4,328,558 tons of shipping, representing 1,299 ships in all; U-Boats had sunk over 2 million tons (432 ships) while surface raiders, aircraft and mines accounted for the rest. But in 1942 the U-Boats alone sank over 6 million tons, while the total losses from all causes amounted to 7,790,697 tons (1,664 ships). It was April 1917 all over again, except that this time all possible counter-measures had been put into effect and yet the U-Boats were winning. In January 1942 the Germans had 91 U-Boats operational, and although 87 were lost during the year, new construction meant that 212 were operational by December.

The scent of victory

Dönitz and his submarines could smell the scent of victory in the air, and he exhorted them to greater efforts. It was essential for the U-Boats to prevent the Americans from bringing their enormous resources to bear on Europe, and Dönitz calculated that it would take a monthly loss rate of 800,000 tons of Allied shipping to starve out the British and prevent the Americans from implementing their strategic plans to liberate the Mediterranean and the Continent of Europe.

The average monthly losses of shipping in 1942 were running at 650,000 tons, which was far beyond the rate of replacement, so the first priority for the United States was to build more merchant ships. With boundless ingenuity and energy American shipyards devised methods of mass-producing ships, and soon "Liberty" and "Victory" standard hulls began to appear in numbers. The British were beginning to see the results of their large warship-building programmes of 1940/41, and in 1942 the first "River" Class frigates appeared, 1,400-ton twin-screw ships with enough endurance to cross the Atlantic and more speed than a surfaced U-Boat. With more radar sets and H/F-D/F sets available for escort vessels the existing convoy escorts were also better equipped to fight off wolf pack attacks, and this was reflected in the large number of sinkings in 1942.

The U-Boats were helped at this time by the so-called "black gaps" in mid-Atlantic, five areas which were out of range of shore- based aircraft. In these areas U-Boats could stalk convoys without the fear of being forced to dive by an aircraft, and they sank many ships with little loss to themselves. The introduction of more escort carriers in the late summer of 1942 and the provision of a handful of VLR (Very Long Range) Liberator bombers helped to close the air gap, but the numbers of both would remain small until 1943.

A useful interim measure was the MAC-ship or Merchant Aircraft Carrier, which was an oil-tanker or grain-carrier equipped with a plywood-flight deck to allow her to operate four aircraft. The virtue of this compromise was that it did not prevent the ship from continuing to carry her valuable cargoes, whereas an escort carrier was completely gutted and converted to a warship. On the other hand an escort carrier operated from 15 to 24 aircraft, and had the . necessary communications equipment for controlling aircraft over a convoy.

The U-Boats continued their grim War of extermination, for their goal of 800,000 tons of enemy shipping sunk per month seemed within reach. Indeed Admiral Dönitz believed that they had reached the magic figure, but as in the First World War, U-Boat commanders tended to over-estimate the tonnage of their victims. As we have seen, the losses did not exceed 650,000 tons, which meant that the collapse of the Allies was further away than Dönitz thought. New torpedoes and devices were coming forward, and it was hoped that these would tip the scale. The most important were the homing torpedo and a radar impulse detector, the torpedo to increase the rate of hits and the detector to reduce the chances of being surprised by ship or aircraft on the surface.

The first homing torpedo was issued in January 1943, and was known as the T4 or "Falke", but after only thirty had been used it was replaced by the better-known T5 "Zaunkonig". This was the weapon known to the British as the "Gnat" (for German Naval Acoustic Torpedo), and it travelled at the relatively low speed of 25 knots to reduce interference from its own noise.

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