Hut Three - The U-Boat Menace

Hut 3 – The U-Boat Menace

The U-Boat Menace

The German U-boat proved to be a deadly weapon against British shipping. Between 9th – 12th September 1941, sixteen British ships were sunk for the cost of only one U-boat. Although vulnerable to an attack when on the surface, these machines were efficient and deadly when submerged.

The U-Boat Offensive

The German Navy adopted ‘Wolf Pack’ tactics during World War II, which was based on the principle of concentration. By operating in an extended search line, hundreds of miles of ocean where covered. This enabled the U-boats to search and attack the convoys much more efficiently. It also offered some degree of security by providing too many threats for the escorts to tackle.

The U-Boat Described

Between 1935 and 1945, Nazi Germany produced twenty-six different types of U-boat. Germany actually went to war in 1939 with only 57 coastal and ocean-going U-boats. This was due to the fact that the ban on German submarines, after the Treaty of Versailles, made the newly formed German Navy of the 1920s and 1930s concentrate on surface warships. Peak production of this deadly weapon was not reached until the last year of the war.

British Submarines in WWII

At the start of the Second World War British submarines were used primarily in a reconnaissance role. This work was undertaken in the southern North Sea and near the Norwegian coast beyond the range of aircraft patrols. This work however met with relatively little success as there were not enough submarines and the winter darkness was too long for them to be effective in sighting German surface units.

Submarine Tracking Room

Of all the various sections within the Naval Intelligence Division (NID), NID 8(S), the Submarine Tracking Room, was probably the most important. This branch eventually controlled virtually the whole of the anti-submarine war and apart from the odd occasion, very few ever dared to question its judgements.


‘Active’ sonar, the submarine detector commonly called ‘ASDIC’ (the initials of the Allied Submarine Detection Investigation Committee who had initiated its development in 1917) was basically a transceiver sending out sound impulses and picking up echoes from the objects it struck. The intention was to identify U-boats, but echoes also came back from shoals of fish, tidal movements and shifts in the temperature of water.

Warship Adoption

During the 1939-45 War it was customary for cities, towns and villages, to organise ‘Warship Weeks’ whereby money was raised through National Savings to meet the cost of providing a particular ship. The cities obviously sought to pay for the big battleships or aircraft carriers, whilst many Towns found sufficient money for cruisers or large destroyers.

Escort Carriers

Merchant shipping was continually at risk during the early years of the war because of the inability of shore-based aircraft to provide more than partial cover over submarine-infested waters. An obvious solution was to provide merchant fleets with portable air cover, in the form of planes based in aircraft carriers. This was the origin of the type of ship named the Escort Carrier.

The Fleet Air Arm

The Fleet Air Arm, administered entirely by the Admiralty, started its independent existence on 24th May 1939, when the Royal Navy took over complete charge of all sea-borne aircraft, whether in aircraft carriers or other warships.


Although America did not enter the war until Japan attacked Pearl Harbour on 7th December 1941, Roosevelt’s sympathies were with Britain. In September 1940, he arranged a deal under which fifty aged American destroyers were given to Britain in return for a ninety-nine year lease of certain air and naval bases.

Merchant Aircraft Carriers

By June 1943, although the German submarines had virtually been withdrawn from the North Atlantic convoy route, it was still deemed necessary to continue close naval support from escort vessels. Air cover, where feasible remained vital. By the end of September 1942 the range of air cover available from Iceland had been increased to 800 miles. In October 1942, the Admiralty ordered that six grain ships, which were under construction, were to be adapted to Merchant Aircraft Carriers or MAC ships, in order to bridge the gap in the Atlantic where shore-based aircraft could not operate. Six tankers were also fitted out with flight decks.

The Merchant Navy at War

At the outbreak of war there were about 21.25 million tons of merchant shipping registered in Britain. The merchantmen were the critical element in the struggle. It was these ships that the men, women and children and every uniformed serviceman depended on for survival. They carried on them food, raw materials and despatches of military forces.

Mine Sweepers

The wartime mine was not a new invention more, the product of four centuries of human ingenuity. During that time scientists have fought an unceasing conflict of wits as one has produced a destructive device and another has countered it.