In September 1939, the Kriegsmarine began submarine warfare with less than thirty operational submersibles. Two years later, following an intense construction effort, Admiral Dônitz was able to launch at least 250 U-boats on a mission, of which around 100 were permanently in operational areas.
The North Atlantic, around the British Isles and Iceland, the coasts of West Africa, and sometimes the South Atlantic represent the attack zones of these submersibles. But in December 1941, after the Japanese attack on the United States at Pearl Harbor (on December 7), then the declaration of war by the Axis powers on the United States (on the following December 11), the area of The action of the German submarines extends this time to the North American coast and the region of the Antilles, where oil tankers mainly sail from Venezuela and the Gulf of Mexico. The number of torpedoes then increased in enormous proportions, because all these boats sailed in isolation.
It was however in October 1942 that the number of torpedoes, according to Winston Churchill (War Memoirs) reached the highest monthly figure of the whole war with the loss of 117 ships weighing more than 700,000 tons. But this same month of October will see the destruction of 16 Axis submarines, a figure which also represents a destruction record. The convoy system, the support of surveillance aircraft from escort aircraft carriers and the improvement of detection means and the armament of escort vessels will finally enable the Allies to ward off the underwater danger.
The Royal Navy's armament plans had taken shape as early as 1936, when Hitler advanced into the Rhineland, thus delimiting the field of his future aggressions. Already at that time it was clear to the British Chiefs of Staff that war was inevitable. In a note sent to the Ministry, they estimated that it would break out in the second half of 1939. After the occupation of the Rhine, a supplementary budget was presented to the House of Commons for the construction of two battleships, a carrier aircraft, five cruisers and several smaller vessels, which was to be followed in 1937 by three more battleships, two aircraft carriers, seven cruisers and an even larger number of smaller vessels. When, in 1939, the English nation entered the war, the first of these newly built boats had just joined the fleet.
The war plans which the British Admiralty published on January 30, 1939 had adopted the principle of a defense strategy. There is nothing like it, in the initial phase of a maritime war, to remain in control of the situation. The will to rush to the attack has been so often the prelude to disaster that it is always prudent to organize and leave it to time to build up sufficient and well-trained forces to go through with it. offensive. It is only when this stage has been reached that an attack strategy can really bear fruit.
The plan for the Royal Navy was based on the presumption that, from the outset, war would be fought, both against Germany and against Italy. This plan was developed in three main parts. The first aimed at the protection of trade in English territorial waters and in the Atlantic. It was fundamental, because refueling is the sinews of war. In second place came the protection of trade in the Mediterranean and the Indian Ocean. It was obvious that, if Italy proved to be a belligerent enemy, its preponderant geographical position in the Mediterranean Basin would force all maritime traffic to take the infinitely longer route of the Cape of Good Hope. It was therefore necessary to neutralize it thanks to a powerful fleet based in the Mediterranean. The third part of the plan was to organize a blockade against the two enemy powers. As soon as war was declared, a list of contraband items subject to seizure at sea was published, even if carried on neutral vessels.
To put the plan into effect, the big of the Home Fleet (the fleet intended to protect the British Isles), was concentrated in Scotland. To the far north, cruisers from the Northern Patrol kept watch. They were ready to intercept any ship, enemy or neutral, heading towards or away from British territory. From the Shetland islands to the coasts of Norway, a surveillance front was organized, half by aerial patrols, half by submarines.
The Home Fleet, 'minus some of its units which were stationed elsewhere, was in Scapa Flow Bay, in the middle of the Orkney Archipelago. From there she could meet any enemy threat that presented itself at sea. in German waters. A squadron of cruisers and a flotilla of destroyers were in the Humber Estuary. To the south, an armada of battleships, aircraft carriers, cruisers and destroyers was based in Portland to watch the exit to the Atlantic.
In addition to the Home Fleet, the four states -national majors, Plymouth, Portsmouth, The Nore and Rosyth, each had their units of destroyers, anti-submarine ships and minesweepers which served for local defense and protection of convoys. They were placed under the direction of the local commanders-in-chief. Given the knowledge acquired at that time, it all seemed to form a network large enough and dense enough to intercept any enemy ship trying to force its way one way or another.
For As for the Mediterranean, it had been agreed that the French navy would hold the western basin. The British fleet was therefore based in Alexandria, in order to operate in the eastern basin and keep control of it. To implement the blockade, the plan called for strong forces in the Strait of Gibraltar and the Red Sea. Moorings were set up there to search merchant ships entering the Mediterranean.
On the German side, the plans were, of course, adapted to a fleet which, at the base, was not ready to go to war. Shortly after coming to power, Hitler confided to Admiral Raeder that he did not want to embark on a general conflict before 1944. It was on this presumption that Raeder planned the expansion of the German navy. When war broke out, many of the ships he would have liked to have had at his disposal were still under construction, if not in the planning stages. He still had a usable navy. The three "pocket battleships", officially from. 10,000 tons to respect the terms of the Treaty of Versailles, but which, in fact, approached 13,000 tons, were already available. The battlecruisers Scharnhorst and Gneisenau, which also exceeded the treaty limits by 6,000 tons, were formidable adversaries. As for the big cruisers of the Admiral Hipper class, they exceeded their weight by some 4,000 tons and were almost finished. He could also have 56 submarines, the U-boats, which were all able to operate, except for ten. Their crews had been well trained during the years when submarines were not allowed, on the pretext that they interfered with anti-submarine drills.
Combat instructions were unveiled at the German fleet in May 1939. The plan called for a continuous series of maneuvers in the North Sea to create maximum confusion there, especially attacks by merchant ships. This was to force many English forces to stick around to oppose these attacks.
All ships of greater tonnage were to cruise the oceans and also make sustained attacks against merchant shipping. The submarines, on the other hand, had the mission of operating against trade in the Atlantic and around the main British ports. To compensate for the delay of the new high-tonnage ships, still under construction, a certain number of merchant ships had to be armed and converted into warships.
In these instructions a small sentence had slipped ominous:“Do not fail to use all forms of combat, even if certain international regulations oppose it. »
It was a foreshadowing of the all-out war that the English had long hoped would be banned for a long time and forever on the sea...
The German Navy made its arrangements in time. On August 21, 1939, taking advantage of the night to cross the North Sea, the pocket battleship Graf Spee slipped into the Atlantic unnoticed. Three days later, the Deutschland, another pocket battleship, performed the same maneuver under the same conditions. The tankers that were to supply them with fuel, the Altmark and the Westerwald, did the same. Between August 19 and 29, 17 U-boats, of the type that were maneuvered in the oceans, were deployed in the areas of the Atlantic where they were to carry out their patrols, while 7 of their counterparts , smaller and specialized in operations along the coasts, received the mission of disposing of mines off the Channel ports. 6 others were given the job of patrolling the middle of the North Sea.
The first task incumbent upon the Royal Navy, was to draw a circle around the enemy, in order to deprive him of the supplies which could only be brought to him by sea. North, as well as along the entire length of the Mediterranean, the maritime forces of the Allies maintained this circle. On the mainland, their ground and air forces established the junction. The only possibility of supply for the Germans remained, therefore, only in the east, where Russia enjoyed a free zone, resulting from its non-aggression pact with Germany.
The effects of this carefully closed circle on the enemy can be judged by the fact that from the beginning of the war until the end of 1939 the Royal Navy was able to seize 530,000 tons of supplies intended for the 'Germany.
Outside this circle, however, the problems were piling up. With war barely declared, Athenia, ship of the Donaldson line, was attacked by the U-30 submarine, about 200 miles west of the Hebrides.
She sank with her 112 passengers. It is certain that the captain of the U-30 had exceeded his orders by sinking this vessel, but this loss was proof to the British Admiralty that a merciless submarine war had just been unleashed.
The provisional arrangements provided for in the plan concerning the protection of trade on the Atlantic were abandoned. This device consisted of patrolling protection boats in strategic areas and engaging merchant ships on different routes. It was decided to adopt the Convoy system as soon as possible.
On this point, the Royal Navy felt acutely the effects of the delay brought, before the war, to the restructuring of the English navy. The destroyers and other buildings available at the time to possibly escort the convoys were not strong enough to push far into the Atlantic. Until the new ships could be delivered and put into service, a "convoy limit" had to be instituted. This limit was fixed at a distance of about 300 miles from the English coast, to the west. Beyond this point, ships in convoy were to disperse and continue on their own. Convoys heading for England were escorted across the ocean by a warship, usually a duly armed merchant ship, and then, at the "limit", they were picked up by authorized escorts who accompanied them to the English ports. Later, when new ships became available, the limit was pushed back. But it was not until mid-1941 that the Royal Navy found itself in a position to provide convoys with effective anti-submarine escort across the entire ocean.
Despite these restrictions, the casualty figure was not too discouraging. Until the end of 1939, U-boats sank 114 ships with a total tonnage of 421,156 tons, but 9 of them suffered the same fate. Considering the limited resistance of the escort forces, these figures were quite satisfactory. Nevertheless, the Admiralty never lost sight of the fact that these results were fleeting and that, from one day to the next, everything could change. It was known that Germany had undertaken a very substantial program of new constructions, which was to double or triple the number of their submarines, by 1941 at the latest. This number was, in any case, to increase gradually throughout the operations. It should not be hidden that, as soon as the force of the U-boats was at its maximum, the losses of merchant ships would be heavy.
Meanwhile, the English tried to go to the attack on the submarines, but their attempt ended in disaster. Two fighter groups had been formed, each consisting of an aircraft carrier and four destroyers. The attack was launched in the west, not far from the English coast. On September 14, Ark Royal was narrowly missed by torpedoes from U-39. The accompanying destroyers counter-attacked. They sank the submarine and took its crew prisoner. But they had a narrow escape.
Three days later, the second hunting party went into action. The aircraft carrier Gourageaous was spotted by U-29 which torpedoed and sank it with its 519 crew members. At this stage of the war, aircraft carriers were particularly valuable ships, since those ordered in 1936 and 1937 could not be commissioned until 1941 at the earliest. The Admiralty immediately decided that it was running a big risk to continue to use them for this kind of operation. The Ark Royal was therefore recalled and resumed its place in the Home Fleet.
An organization was growing within the Admiralty to coordinate the fight against submarines. Before the war, an intelligence center had been founded to study all the information of an operational nature that could be obtained, to judge it at its fair value and to transmit it to the fleet.
As far as the U-boats were concerned, a "tracking" service was created to which all information relating to their activities was entrusted. Reports from agents stationed in enemy country, giving details of departures and arrivals, sightings of submarines by planes or ships, attacks launched by the submarines themselves and, the most fertile source of all, the radio position of each message transmitted at sea by a U-boat:all this was directed to the intelligence center. The tracing service was linked by teleprinter to each listening station. No sooner had a U-boat used its radio than its bearing was immediately recorded. By comparing it on a map, the exact position of the submarine could then be determined.
In addition to this tracking service, the "traffic plot" was used, which showed the position, the course and speed of each convoy and single vessel. Thanks to this, it was possible to determine the position of the submarines in relation to the convoys and to avoid accidents to the latter, by signaling to them the dangerous zones. The convoys could then change course. The tracing and tracing service operated night and day. Gradually, it was possible to predict the movements of submarines more and more easily, and the effectiveness of the tracking service became so great that, around 1943, more U-boats were sunk than these reached. to sink English ships.