Battlefield application of wolf pack tactics: German submarine warfare finally faces failure.

Even in this period dominated by large surface warships, smaller U-submarines still sank a large number of allied ships. The captains of German submarines called this period "happy time". The great success of the U-shaped submarine stems from the application of new tactics and careful study of the key weaknesses of the Allied transport fleet. In the first year of the war, many ace captains emerged in the German navy submarine force, such as Oddo Klaz Mo, Gunter Prien, Joe Jim Sepke and Frith Lampe. They command U boats to attack independently, and each boat can sink an average of 25 allied ships every month. However, Deng Nici believes that assembling a large number of submarines to attack the fleet protected by escort ships can further develop the characteristics of U-shaped submarines and expand the attack effect.

This view is simple. However, if the U-submarine wants to attack the transport fleet in the open sea, there are three key problems: the first is to find the initial position of the fleet, the second is to assemble around the fleet, and the third is to really attack. Deng Nici's plan is to organize the submarine into several units, each unit is deployed along a straight line perpendicular to the fleet route, and at the same time, the actions of each unit are commanded by the radio of the headquarters. During the day, submarine commanders send their position information back to the submarine command in Deng Nici at noon, and report the weather if necessary. In turn, the headquarters commander informed the submarine commander to adjust the position of the troops according to the latest information.

If all goes well, a submarine detachment can intercept a transport fleet and report its position, course and speed. Although the submarine can locate the mechanical noise of the ship through the sonar device, it can only find the target within the visual distance. With the development of war, the sonar performance of U-shaped submarine can be almost comparable to that of the radar of escort ships. This is simply a competition between the commander of the allied fleet and the commander of the German submarine. Because it is often the most difficult to find the target, many times, the fleet passes through a submarine patrol unit without being found.

Once the U-submarine finds the target, it immediately hides, monitors and tracks the fleet. At the same time, timing signals are sent to other boats to report the position, and intermediate frequency direction finding signals are also sent for direction positioning. After receiving the signal, the other submarines of the detachment immediately moved closer to the fleet. U-boat combat orders stipulate that each submarine must track and record the reports of other submarines finding targets. Although in this process, the frequent radio communication between submarine forces is very easy to be intercepted by DF base stations on the coast, Deng Nici still firmly believes that this tactic is very safe to use.

It is very important to collect information by listening to the direction finding signals sent by German submarines at sea. After carefully studying the transmission mode of these signals, the Allies have accumulated some important data. By analyzing the direction finding signals intercepted by land base stations, we can roughly estimate the number and approximate location of German U-submarines at sea. The function of this wireless communication traffic analysis technology is very obvious. But in 1939, the land base station can only estimate the submarine position within 50 miles, and no one can design and invent a direction finding signal monitoring device small enough to be installed on a ship, so the information collected by the allied direction finding signal monitoring has no tactical function. In any case, the attack of the U-submarine directly exposed their existence, and they only relied on the monitoring of radio communication when they had to. So 1940, Germany has an absolute advantage.

The radio signal of the submarine is encrypted with a highly complex Enigma cipher machine. Each cipher machine has a series of letter rotors and plug wires connected to the plug board. Modify the rotating position of the rotor and the connection mode of the patch panel according to the password book every day. Therefore, when the operator taps a number or letter on the keyboard, another completely different number or letter will be displayed on the screen. Three or four groups of rotors, with different plug-in methods, can produce tens of millions of possible letter combinations. Deng Nici knows very well that the signal encrypted by Enigma cipher machine can be cracked, but it is very time-consuming to completely crack it. Therefore, the signal cracked in a short time is quite limited, which is not enough to affect the operational deployment of submarines.

In the last formation attack launched by the U-shaped submarine, the submarine was very loose and could only keep in touch by radio. The attack earned them the nickname "Sea Wolf". Before ordering the dispersed attack, Deng Nici assembled as many U boats as possible to surround the transport fleet, which was a near-perfect "wolf pack operation". Every submarine has no tactical cooperation because it is impossible to cooperate in that environment. So according to the conditions at that time, I decided to attack from the darkness of the fleet at night. The submarine used the black night sky as a cover to approach quietly, while the allied fleet appeared chiseled in the moonlight. Attack after attack. The submarine dived to the most suitable depth for attack, only revealing the control tower. They quickly broke through the defensive circle of the escort ship and went straight to the transport fleet. The purpose of high-speed impact is to fire all four pairs of torpedoes at the bow and, if possible, two at the stern. After all the torpedoes are launched, the submarine will retreat to the end of the fleet or dive in the chaos left by merchant ships.

1940 autumn, the new wolf tactics made full use of the fatal weakness of allied maritime transportation. At this point, coastal areas have become the main sea areas threatened by U-submarines. These submarines usually act alone and stay underwater when attacking. Therefore, anti-submarine escort ships are deployed on both sides of the Atlantic. In the middle of the vast Atlantic Ocean, the fleet sailing eastward is protected by cruisers, old battleships or allied submarines. Once the fleet sailing to the west left the designated dangerous sea area infested by German submarines, it spread out and sailed alone. Therefore, the transatlantic fleet is particularly vulnerable to U-submarines when sailing in the sea without escort protection. The escort itself can only deal with one submarine at a time.

Countermeasures

1940 16 On June 16, six U boats intercepted and attacked the fleet numbered SC7, but the attack was not satisfactory. This slow fleet from Canada consists of 34 ships, accompanied by three anti-submarine frigates and RSAF's S25 Sunderland long-range water bomber. In fact, the U-48 submarine sank two transport ships immediately after discovering the fleet for the first time, but was immediately expelled by the bombers. So Deng Nici reorganized a submarine formation and launched an attack the next night. What happened next was similar to the violence when sharks were eating. Even the Germans can't figure out what they did-five submarines actually walked between ships at will. By the end of the attack, 22 ships had been sunk, which was the highest loss rate among all fleets in the North Atlantic during World War II. 10/0 On October 20th, a new formation including five submarines (several of which participated in the attack on the SC7 fleet) attacked the allied fleet numbered HX79 again. Although 1 1 many warships escorted the fleet, including two destroyers and three light cruisers, it sank 12 transport ships.

The U-shaped submarine's wolf pack action made the allies suffer in the winter of 1940- 194 1, but the allies quickly made clear countermeasures. The most important thing is to invent the radar that can be installed on small warships and aircraft, especially the latest radar device with the emission wavelength of 10cm, which can detect the high-frequency direction finding signal receiver on U-shaped submarines and ships. In February this year, the Royal Navy moved the Western District Command from the south of England to Liverpool, with full command of the North Atlantic merchant ship escort mission. They can use the RAF's coastal combat aircraft to participate in anti-submarine operations in the war zone. In addition, Britain also built a naval and air base in Iceland, expanding the scope of anti-submarine escort to the middle of the Atlantic Ocean. 194 1 On March 6, 2008, Churchill announced that Britain was determined to invest more strength to win the war in the North Atlantic.

At the same time, the Western Command clarified the composition of the escort fleet, the leadership system and training methods of the fleet, and studied the standardized tactical anti-submarine warfare laws and regulations. 194 1 April, the first tactical manual-guiding principles for escort operations in the western theater was released. According to this principle, the first task of the escort fleet is to escort the transport fleet to its destination safely and timely, and the second task is to sink the German U-submarine.

At the same time, the anti-submarine warfare capability of the escort fleet has been continuously enhanced, the weather has been greatly improved, and the performance of the British radar has also improved a lot. These favorable conditions laid a decisive foundation for Britain's victory in mid-March. In that battle, two large U-boats, Prien and Skepke, sank at sea, while the other Kratzmer was captured by the Royal Navy. The loss of these three submarines marks the end of the "happy time" of the U-shaped submarine. The Schanhost and Nesselau withdrew to the port of Brest in France, and the threat of German blockade to cut off the British Isles was also lifted. 1941April, the United States announced the expansion of neutral waters. The new sea area includes Iceland and most of the mid-Atlantic, which makes the anxious British feel more at ease. At this point, the US Navy's escort covers half of the North Atlantic, and at the same time, it can safely broadcast the positions of allied fleets and aircraft through open channels.

194 1 spring, the operation of providing anti-submarine escort for the mid-Atlantic transport fleet officially ended. In June of the same year, the newly formed Royal Canadian Navy established a base in Newfoundland. From here, the Canadian escort fleet can go directly to Iceland, where it will hand over the transport fleet with the British fleet. This fills the last vacancy on the fleet route. The Royal Canadian Navy escort fleet in Newfoundland has several newly built light cruise ships, some old destroyers retired by the US Navy (the crew are all novices), and a few high-performance destroyers, so the combat effectiveness is relatively weak. But the commander-in-chief of the Western Command said: "This can basically solve the safety problem of the fleet in the North Atlantic." Nobody wants them to meet a German submarine. 194 1 in the summer of, the British made a major breakthrough in the process of deciphering the encrypted information of Enigma, which almost guaranteed that the fleet would never face any danger from U-submarines at sea again.

Wolves in the mid-Atlantic

By May, in the A3 escort fleet, the US Navy had only a few lightly armored ships and destroyers of the Coast Guard. This escort fleet is nominally an American fleet, but it is mainly composed of Canadian light cruisers. The Royal Canadian Navy once again took over most of the Clippers' escort missions, and most of the combat troops under the 24th Fleet were Canadians. As Iceland is no longer used as the escort handover place, the fleet must fly directly between Northern Ireland and Newfoundland. As long as the fleet sails in a straight line, and these light cruisers and destroyers are not very keen on attacking German submarines, safety can basically be guaranteed. However, contrary to expectations, German submarines made full use of these potential opportunities and launched several attacks in the late summer of 1942.

General Deng Nici found that the merchant fleet was sailing on the huge loop route near the far north, and their escort fleet was very weak. Therefore, he transferred the main force of the submarine force to the middle of the Atlantic for standby operations. The Canadian escort fleet still guards the slow fleet, and they have not installed more advanced shipborne radar devices. The first generation radar on the ship is easy to be found by the latest radar signal detector on the U-submarine, and there are too few destroyers in the escort fleet-destroyers are fast, which is of great significance in anti-submarine warfare. At the same time, only one Royal Canadian Navy frigate in the whole fleet is equipped with the latest direction finding signal monitoring device. What's more, since February, the allied forces have been unable to accurately analyze the radio communication traffic of German U-boats. With the rapid increase in the number of submarines in the mid-Atlantic, the battle has reached an important turning point.

1942 autumn, the double encounter finally broke out. After a series of naval battles, the Canadian navy was defeated and retreated from the middle of the Atlantic Ocean. From July to the end of 1942, although the fleet escorted by Canada only accounted for 30% of the total, and almost all of them were slow ships, the lost ships accounted for 80% of the total losses of the allied forces in the same period. Britain immediately condemned the incompetence of the Canadian navy, but without the tactical support of high-performance radar, the Royal Canadian Navy could only fight blindly.

In order to solve this problem, people put forward some improvement measures, such as launching flares in advance to help find and prevent submarine attacks. But this method was stupid and dangerous, so it was soon given up. In contrast, the development of a fast fleet, escorted by well-equipped British warships, will be much better. The latest direction-finding signal monitoring device on the British destroyer can intercept the electric waves emitted by the U-shaped submarine on the sea surface, forcing the nearby German submarine to dive below the sea surface, thus interrupting the contact with the outside world. At the same time, the British Navy's 10cm radar can build a solid defense network for the entire fleet at night. With advanced weapons and accurate tactical information, the British navy blocked the siege of "wolves" and lost ground, eventually sinking the U-shaped submarine.

1 1 In June, 2006, in a battle to protect the fleet numbered SC 106, the Canadian fleet suffered a fiasco-15 was sunk. After that, Britain began to deploy in June+early February, 5438, allowing the Canadian navy and several remaining American warships to withdraw from the Atlantic theater and no longer providing escort protection for the transoceanic fleet. The A3 fleet's record in the middle of the Atlantic is not as bad as that of the other four Canadian fleets, but its equipment is as backward as that of Canadian warships, and the speed of the Sektree class light armored ship is too slow. Of course, there are other reasons.

Since 194 1 handed over the control of the western Atlantic route and increased fleet command to the United States, Britain has been miserable. Moreover, at the end of 1 1, due to the need to support the allied landing operations in North Africa, Britain suspended its anti-submarine escort operations in the eastern Atlantic. Britain will not only fight side by side with the whole world, but also cross the mid-Atlantic alone with the U-boat. Therefore, Britain took over the operational command of the entire Atlantic campaign. 1942 65438+ 10, Canada withdrew from the battle, and the A3 fleet was ready to disband. At this point, it fell to the British to provide escort for transatlantic merchant ships.

At the beginning of 1943, the Royal Navy assumed the main responsibility of escorting the fleet in the North Atlantic, and the middle of the Atlantic became the last "hunting" place for the seventh generation of German U-submarines. The German navy hopes to win some kind of strategic victory. At the beginning of 1943, 100 many U-shaped submarines were cruising in the waters in the middle of the Atlantic Ocean, which exceeded the operational scope of the conventional land-based fighters of the Allied Forces. It is almost impossible for the fleet to avoid them. 1943 10 and February, some progress was made in cracking the communication code of the u-submarine, so the allied fleet entered the sea area again. However, just like what happened to the Canadian fleet in autumn, as long as the slow fleet leaves the protection range of friendly fighters, once it encounters 20 to 30 submarines, its fate will be very tragic. In June+10/October, 65438, in order to protect the fleet numbered SC 1 18, the British Royal Navy's escort fleet launched a fierce battle with German submarines. In this campaign, the allies sank four U-boats, and they lost 1 1.

1On February 20th, 943, the Germans intercepted important information, and the allied slow merchant fleet numbered ONS 166 will cross the Atlantic Ocean westward. Subsequently, the U-boats were ordered to gather in the middle of the Atlantic to stand by. The A3 fleet providing escort for the fleet consists of American light armored ships Spencer (WPG-36) and Campbell (WPG-32), Canadian light cruisers Rosen, Kilim, Dove and Hollywork, British light cruiser Ti Annsas and Polish destroyer Buze. After the first U-submarine found the fleet, it retreated immediately for fear of being found by direction finding detection equipment. The next day, a long-range bomber of the Royal Air Force 120 squadron sank a submarine. However, as the fleet gradually moved away from the air force's protection, German submarines stepped up their offensive. 2 1 night, the U-shaped submarine broke through the outer defense of the escort fleet. Although the Campbell sank a submarine, due to the bad weather at sea, German submarines attacked one after another, making it almost impossible to organize effective defense. On the 24th, Canada's improved Kate Lena patrol aircraft flew in for reinforcements, wounding two German submarines in one fell swoop and repelling most of the rest. But the German submarine hid in the dense fog and continued to attack the fleet. Two days later, the brutal fighting ended and the allied forces lost 14 ships.

A series of fierce escort operations in March once again proved that even a powerful heavy fleet could not safely escort the merchant fleet to the destination on the other side of the Atlantic. Allied forces have been using the signal code used by U-boats to report weather conditions as the key to decipher the radio communication when Germans deploy attacks. Once the Germans changed the coding method, the allied intelligence agencies could no longer obtain the necessary information to formulate a fleet route that could avoid a large number of German submarines lurking in the middle of the Atlantic. In the first three weeks of March, all the fleet routes were intercepted by Germany and half of them were attacked, with a loss rate of 22%.

In the attack on the fleets numbered SC 122 and HX229 from March 6 to March 20, the German navy won the most brilliant victory. More than 40 U-boats participated in the attack, which was the biggest "wolf pack" operation during the whole World War II. The attack lasted four days. Although the Allied forces combined two fleets and strengthened the escort force, 2 1 ship was sunk by German submarines. In late March, due to the very strong wind at sea, the allied merchant fleet was able to escape the fierce attack of the U-submarine. By the end of March, 7 1 allied ships were sunk in the middle of the Atlantic Ocean.

Wolf's failure

However, by the end of March, everything had changed. The Allies reached a resolution to hand over control of the North Atlantic 47 degrees west of the British Isles to Britain. From March 30th, 1943, all operations in the mid-Atlantic were under the unified command of Britain. The Allies not only dispatched several long-awaited aircraft carriers and more long-range combat aircraft to strengthen the anti-submarine force in the sea area, but also set up a strong reserve force to provide effective maritime support in time. In addition, allied cryptographers cracked the German code, enabling the Allies to design a safer route. At the same time, by listening to the radio communication of German submarines, we found that their morale was very low-the time was ripe for a counterattack. More importantly, the weather on the sea surface has been greatly eased, and there are many fewer storms, which makes it more efficient for destroyers to use radar and direction finding equipment to clean the sea surface. The British general command made full use of these conditions, opened up a safe route far away from the latent area of German submarines, and transported a lot of materials. At the same time, the powerful anti-submarine fleet was sent to the encirclement of the U-shaped submarine as bait-the time to slaughter the "wolves" finally came. British tactics finally worked, breaking the myth of "wolves". At the end of April, the British fleet met a German submarine while protecting a fleet of 46 ships, numbered ONS5, sailing from east to west. On April 28th, 1943, a German submarine found this fleet, but was immediately driven to the south of Iceland by the US Navy Katrina bomber who came to reinforce it. The fleet struggled to resist the attack of U-boats, and they were in urgent need of support. At that time, the information was not very accurate, and some guessing skills were needed when making the route. At the same time, the intelligence department of the German navy cracked the communication code of the allied fleet, so at least 40 U boats were assembled in the sea area in front of the ONS5 fleet. From April 29th, 1943 to May 29th, 1, there were intermittent allied planes taking off from Iceland and Newfoundland to support the fleet. Newfoundland warplanes attacked the westernmost submarine in Germany and sank one. Four destroyers of the Royal Navy's Second Reserve Fleet also joined the battle on May 2nd and 3rd 1943, and did not leave until refueling.

Although the fleet route was successfully designed and the pilots of long-range fighters fought bravely in bad weather, they still failed to prevent the U-submarine from attacking the ONS5 fleet again on May 4th. Because the number of escort ships is much less and the defense force is seriously insufficient, six merchant ships were sunk at night. On the 5th, the German submarine sank four more ships under the cover of bad weather, but the fighters supported by the Allies did not find the fleet. As night fell, there were only seven escort ships left, and the fleet was inevitably surrounded by 15 German submarines.

Fortunately, however, in the early morning of the 6th, these seven warships were looking forward to the timely reinforcement of the Royal Navy 1 escort fleet. At the same time, there is fog on the sea, which is a great opportunity for the 10cm radar on the Royal Navy destroyer to play its role. When the U boats groped around and couldn't find the target, the escort warships searched German submarines one by one and sank them. At sunrise, the convoy sank five submarines. In addition, two submarines collided and sank while searching the fleet. After a night of melee, the Germans lost seven submarines, and Deng Nici had to give up the attack.

The allies completely abandoned the evasive strategy. Throughout May, allied warships have been actively searching for and attacking German submarines, and many U-shaped submarines have been "slaughtered". The Bay of Biscay is the only place where U-boats pass. Here, 50 allied air force fighters launched a fierce attack on the submarine and achieved great victory. In May alone, the Allies sank 465,438+0 U boats and lost only seven merchant ships. 1943 On May 24th, General Deng Nici was forced to admit defeat and recall the "wolves". Whatever the purpose, the North Atlantic campaign is over. 1943 The loss of merchant ships plummeted, and the construction of new ships soared. This year, the traffic volume of new ships reached140,000 tons.

During the whole summer of 1943, the U-submarine tried to continue its attack in the southern North Atlantic from the Caribbean to North Africa, and with the support of the fuel supply ship, it expanded its operational scope. However, the Enigma code used by German submarines has been cracked, and their whereabouts are completely exposed in front of the allied forces, and they have completely become the prey of the anti-submarine fleet composed of aircraft carriers of the US Navy. In September, the German navy installed heavy air defense weapons and newly developed acoustic guided torpedoes on the U-shaped submarine, ready to launch the Atlantic offensive again, but all ended in failure.

By the end of 1943, it was difficult for U-boats to use the "wolf pack" tactics in the Atlantic Ocean. They can only fight independently and can't send out radio signals to avoid exposing themselves, which makes them a real submarine. Although German submarines have been cruising at sea for the last 18 months at the end of World War II, they can no longer pose a threat to the Allies.