After the United States declared war on Japan in December 1941, it changed its policy of avoiding public military action against the United States.

On December 9, the German naval operations department cancelled the decision to deal with American ships with restraint, no longer restricted all actions against American merchant ships and warships, and allowed submarines to search and attack all targets in any sea area of the Atlantic beyond 26 degrees west longitude, including the Pan American security zone.

From then on, the German Navy began unrestricted submarine warfare on the Atlantic line of communication.

The German command believes that the United States’ participation in the war is bound to greatly enhance the war strength of the allies.

However, as long as the German Navy continues to attack the vital Atlantic maritime transport line of the allies, it can weaken its war strength.

The most effective means to achieve this goal is submarine.

Based on this understanding, the German command decided that the naval operations after 1942 should continue to strengthen submarine attacks, eliminate the Allied escort convoy shuttling across the Atlantic, and stop the growth of Allied soldiers and equipment.

Accordingly, the German Navy further stipulated that the main task of the submarine fleet is to engage in “tonnage war”, make use of the favorable conditions of submarine war as much as possible, and make the allied countries lose more than their shipbuilding tonnage in the shortest period of time, so as to weaken the allied countries’ transportation capacity and paralyze their maritime transportation.

Based on the above considerations, the German command and the German Navy plan to expand the operational area of the Atlantic Ocean.

On December 12, 1941, Germany decided to launch the “drum beating” campaign and sent submarines deep into the coast of the United States to launch attacks.

In order to meet the expanding operational needs, Germany further stepped up the manufacturing and deployment of submarines.

In January 1942, the German Navy had more than 260 submarines, of which about 50 of the 100 submarines were concentrated in the Atlantic battlefield.

By June, the total number of German Navy submarines had increased to 330, and nearly 100 submarines had been put into the Atlantic transportation line.

At this time, Germany can produce an average of 18.

5 submarines per month, exceeding the monthly average loss of 7.1. The German Navy plans to increase the number of submarines in service to 400 by the end of the year.

At the same time, the quality of German submarines has also been continuously improved.

The test of the new “Walter” submarine powered by gas turbine has been successful, and the underwater speed can reach 23 nautical miles per hour.

The submarine is also equipped with TS electric and self guided torpedoes.

In March 1942, Germany began to use a large oil submarine called “cow” to refuel the submarine at sea.

With 430 tons of oil, this oil submarine can increase the stay time of 12 medium-sized submarines at sea by 4 weeks, or increase the stay time of 5 large submarines by 8 weeks.

With this “cow”, German submarines can go deep into any sea area of the Atlantic Ocean, and their combat capability and participation rate have increased greatly.

The Atlantic sea line is the lifeline of the allies.

Ensuring the smooth flow of this traffic line occupies a very important position in the strategic plan of the allies.

It is related to the survival and safety of Britain and the success of the offensive campaign of directly counterattack against Germany in Europe.

However, by the end of 1941, the condition of this transportation line was very bad.

Due to Germany’s Maritime War, Britain’s material imports began to decline sharply.

Admiral Dudley pound, the British admiral, exclaimed, “if we lose the naval battle, we will lose the whole war.

” From December 22, 1941 to January 14, 1942, the United States and Britain held the Acadia conference.

Under the guidance of the strategy of “Europe before Asia”, they determined the strategic plan for the Atlantic and Europe in 1942, and stipulated that the primary task was to concentrate the main force to ensure the maritime traffic of the Atlantic.

After the Acadia meeting, the United States and Britain timely adjusted their domestic systems and policies and accelerated the pace of cooperation.

The United States adjusted its national military command structure and established a joint chiefs of staff corresponding to the British Committee of Chiefs of staff.

On February 6, 1942, the Joint Chiefs of staff of the United States and Britain was established in, which was responsible for formulating and guiding the grand strategy of the American British alliance, thus laying a solid foundation for the joint operation of the United States and Britain on the Atlantic battlefield.

At the same time, the US Navy was reorganized.

Admiral Kim took over as the Secretary of naval operations, Admiral Nimitz took over as the commander of the Pacific Fleet, and Admiral Ingersoll took over as the commander of the Atlantic Fleet.

In view of the confusion in the division of responsibilities between the Secretary of naval operations and the commander in chief of the U.S. fleet, in March 1942, the president merged the two positions under the unified command of admiral Kim.

The naval operations department has changed the naval military region originally under the administrative organization into a combat command organization, the coastal command, to command operations in the sea areas under their respective jurisdiction, and established the eastern coastal command, the Gulf of Mexico coastal command, the Caribbean coastal command, the Panama coastal command, etc.

In addition, the United States and Britain also identified the main task of protecting maritime traffic in 1942 as the elimination of “blank spots”, that is, to carry out regular patrols in the sea areas not taken into account in the Atlantic Ocean.

For this purpose, they transferred escort aircraft carriers.

In order to strengthen the combat power against German submarines, the industrial systems of the United States and Britain have turned to manufacturing ships and aircraft for anti submarine operations on a large scale.

However, due to the limitation of production cycle, these weapons and equipment can not be put into combat in large quantities before the end of 1942.

Therefore, in the summer of 1942, the strength of the allies that could be used in anti submarine operations in the Atlantic was not enough.

There were one American escort aircraft carrier, 183 fleet destroyers and escort destroyers, and 33 submarine hunting vessels.

205 destroyers and escort destroyers, 91 escort ships and 200 submarine hunting ships of the British fleet.

39 US submarines and 61 British submarines.

There are 540 British shore based aviation aircraft and 100 American combat aircraft.

Although the Allies listed the Atlantic operation as the focus of the 1942 battle plan and took a series of measures, due to some problems in the United States and Britain, the two sides failed to cooperate effectively in time.

In 1942, Britain adjusted and reorganized the national wartime system in response to the outbreak of the Soviet German war, the Pacific War and the situation of the United States participating in the war.

There was a heated debate between the British navy and the air force over the allocation of aircraft.

The domestic “overestimation of the potential of the air force” led to the transfer of bombers belonging to the coastal defense command to the air force, and all new aircraft were allocated to the air force.

The naval aviation took great pains to win fighters for the 31 escort aircraft carriers to be put into service, which significantly affected the Navy’s operations in the Atlantic Ocean.

The German Navy broke through the English Channel in mid February“Submarine tactics in Central America.

Due to the long operational distance and difficult replenishment in the waters of North and Central America, close to the coast of the allies, and the complex sea area, it is not suitable to concentrate on the use of a large number of submarines.

Therefore, the German Navy adopts the single boat mobile attack strategy.

The vast waters of the North Atlantic and the long detention time of the Allied transport fleet at sea make it convenient for German submarines to gather and hide and launch continuous group attacks.

Therefore, the German Navy adopted the so-called “wolf pack” tactics in the North Atlantic operation, that is, in the sea area where the transport fleet of the allied countries may pass, gather multiple submarines to ambush, bite the target and attack in groups until the transport fleet is destroyed or enters the area with strong anti submarine force of the allied countries.

At this time, Germany has a large number of troops to implement this tactic.

Dunnitz owns more than 300 submarines.

In September, the number of German submarines in the Atlantic Ocean reached 100 for the first time, and the number of submarines in the operational waters increased from 20 to 30 to 40.

The submarines were deployed at the East and West ends of the “black trap” in the middle of the North Atlantic, and one or two patrol lines were established, 50 to 100 nautical miles away from each other.

The distance between the reconnaissance boats is 30 to 40 nautical miles, which is almost twice the distance of the escort transport team found by the submarine.

Once the central patrol line finds the target, it can quickly concentrate 15 to 20 submarines to deal a heavy blow to the Allied escort transport team.

In September 1942, a German reconnaissance team composed of 10 to 12 submarines and a commando team composed of 18 to 20 submarines operated in the North Atlantic.

On September 11, the u-133 submarine in the reconnaissance team found the Allied escort transport team, followed it, and continuously sent the intelligence of the escort transport team to the assault department through the shore submarine command.

After dusk, five or six submarines quickly concentrated on the escort transport team to launch torpedo attacks, which lasted until dawn the next day.

In this way, the attack was carried out for three consecutive nights until the convoy entered the submarine defense zone along the British coast.

From August to October 1942, the average number of transport ships sunk by submarines of the Allies was more than 500000 tons per month.

With the growth of the total number of submarines in service in Germany, the attack of the fleet on the Allied escort transport team is also more rampant.

They focused mainly on the central part of the North Atlantic, which lacked air cover, and strengthened the coordinated operation of assault boats and reconnaissance teams between Iceland and the Azores and between Iceland and Newfoundland.

In 1942, the Allies lost nearly 2000 ships, of which 1160 were sunk by submarines.

In that year, only about 7 million tons of new ships were commissioned by the allies.

In early 1943, the British Navy increased the number of escort ships, and oil tankers began to sail with the transport team to refuel the escort ships at any time.

In late January, the German Navy successfully attacked the convoy “nx-224” and the slow convoy “sc-118”.

But in January, the tonnage of transport ships sunk by submarines dropped to 200000 tons.

The tonnage of the “ons-166” submarine group sank again in late February.

In March, the tonnage sunk by submarines rose to 627000 tons.

A submarine battle in mid March was the largest during the Second World War.

At that time, the German Navy concentrated 38 submarines and jointly attacked two return convoy transports “hx-229” and “sc-122”, which happened to drive together.

Before the British Navy resumed air cover, the German army sank a total of 21 ships and lost only one submarine, which formed the climax of the Atlantic naval battle.

At the same time, Hitler assembled the German Navy’s large surface ships “tirbiz”, “Admiral Scheer”, “lutov”, “shankhost”, “genezenau” battleship and “admiral Hippel”, “Prince Eugen” cruiser, as well as 17 submarines and some air forces in Norwegian waters, In the Arctic sea area, a broken battle was launched against the cargo ships transporting materials from the allies to the Soviet Union.

Since March, the Allied convoy has been attacked from the air, water and underwater, and the losses are increasing day by day.

From March 28 to 29, German submarines, aircraft and three destroyers attacked the convoy pq-13, sank and injured 10 ships, and injured the convoy cruiser Trinidad.

Germany lost only one destroyer.

From March to June, the German Navy sank 23 of the 84 ships and several warships of the Allied convoy “pq-12” to “pq-16”.

The breaking battle of the German Navy in the Arctic sea has restrained the British and American naval forces.

The US Navy then dispatched the aircraft carrier Hornet, the new battleships Washington and North Carolina, as well as two light cruisers and a destroyer squadron to participate in the escort.

On June 27, the Allied convoy “pq-17” set sail from Iceland to the northern port of the Soviet Union.

The transport team includes 33 transport ships, one oil tanker and three lifeboats.

In addition to the ships directly escorting, the escort force has been strengthened in Iceland.

The transport team has a total of 33 transport ships, including one escort aircraft carrier, one air defense cruiser, 16 destroyers, two submarines and several small ships.

This is an escort transport team with strong weapons and equipment.

However, they were still attacked by German submarines and “junker-88” and “henkel-iii” aircraft on the way.

From September 13 to 20, the escort transport team was attacked by hundreds of German torpedo planes and bombers, and was attacked by German submarines near Svalbard Islands, resulting in the loss of 13 transport ships and one lifeboat.

Due to the strong British escort force, the German Navy lost 3 submarines and about 40 aircraft.

Due to heavy aircraft losses, the German army has no longer invested such a large air force in the north of the Soviet Union.

From October to early December, the Allies dispatched a large number of destroyers to participate in the “Torch” plan.

The British Admiralty and the US Admiralty decided to send a single vessel with alert capability to sail to the northern Soviet Union by taking advantage of the long winter night.

Nine of the 37 dispatched vessels were sunk.

In mid December, the United Kingdom and the United States again sent small escort transport teams to carry out escort by starting alternately from the ports of Iceland and the northern Soviet Union.

The convoy was changed to code “jw-51a”, set sail from loheyiwu and safely arrived at the northern port of the Soviet Union.

On December 31, “jw-51b” sailed to the southeast of Bear IslandThe German army has never cut off the traffic between the old and new world in March 1943 Some in the Admiralty even questioned whether the convoy could continue to be an effective defense system.

After the climax of the submarine war, the Allies were determined to adjust the escort forces, often using aircraft carriers to strengthen the vigilance of the escort transport team, or using shore based aircraft as escort.

In late March, the support fleet organized by British admiral Max Horton played a great role in anti submarine operations.

The six allied support fleets worked closely with the convoy fleet.

When the convoy ships entered the air cover gap, the support fleet went to provide support and gave a more powerful and concentrated counterattack to the German Navy submarines in the middle of the Atlantic.

Destroyers and frigates operating alone in the support fleet can pursue German submarines.

In the last 10 days of March, these support fleets showed their effectiveness.

On March 21, the “s-123” and “hx-23” transport teams ran into a strong German submarine group in the “air gap” southeast of Cape fairwell.

On the evening of March 26, several transport ships of the “sc-123” transport team sailed into the middle of the boat group and were found by German submarines “u-564” and “u-663”.

As the u-663 submarine was soon discovered by the high-frequency direction finder of the third support fleet, it was forced into the water by the support fleet before reporting the course and speed of the transport team.

When there were signs that there were no more submarines around the “sc-123” transport team, the support fleet returned at full speed to meet the subsequent “hx-230” transport team.

Dunnitz ordered the submarine group in the south to attack the “hx-230” transport team at full speed north.

As a result, it was found by the high-frequency direction finder of the support fleet, driven by the destroyer and retreated.

Due to the increased losses caused by Allied aviation to German submarines, the German Navy has taken a series of measures to strengthen the self-defense capability of submarines.

For example, the submarines were equipped with quadruple mounted anti-aircraft machine guns, improved 37 mm anti-aircraft guns, equipped with devices to interfere with radar work, and covered with a layer of special material on the hull and command room of some submarines to partially absorb electromagnetic waves.

In addition, technical observation instruments have been improved and equipped with silent homing torpedoes.

At the same time, the German Navy also adjusted the anti escort campaign tactics and adopted a series of new attack tactics and evasion methods.

However, these new methods failed to reverse the impending failure of the German submarine war.

The strength and equipment of the allies to protect the traffic line far exceeded the German offensive strength in quantity, especially in quality.

The aircraft and surface ships of the United States and Britain are equipped with new radar, the range and endurance are increased, the sonar equipment has also been further developed, and the navigation formation of the escort transport team and the whole escort service have been improved.

The Allied convoy across the Atlantic was almost covered by aviation troops and convoy ships during the whole voyage.

In particular, the assault force of direct convoy ships and aircraft was strengthened, which made it difficult for German submarines without air cover and lack of coordination of other forces to approach the convoy from the surface in the daytime or at night, so they had to approach the convoy from underwater.

The low underwater speed has greatly affected the combat effectiveness of German submarines.

In late March, the number of ships sunk by the allies in the Atlantic decreased from 92 and more than 530000 tons in March to 45 and more than 250000 tons in April.

After May, the losses decreased significantly, while the German submarines suffered heavy losses.

According to statistics, from January to March 1943, Germany lost 3.

8 submarines for every 100000 tons of merchant ships sunk by the allies.

From April to June, it increased to 10.5. In early April, the number of submarines fighting in the Atlantic decreased because only one submarine tanker in Germany could supply oil to submarines and a number of submarines had to be overhauled.

Since April, the United States has strengthened its air force in the Atlantic sea area and dispatched a large number of “liberator” bombers from the Pacific battlefield to fight in the North Atlantic sea area, raising the number of ultra long-range aircraft in this sea area from 20 at the end of March to about 70 in May.

These aircraft are based in balikili in Northern Ireland, Reykjavik in Iceland, gangdia and argensha airport in Newfoundland, and their activities have gradually covered the “air gap” in the Southeast Atlantic Ocean of Cape fairwell.

In this way, the allies can send aircraft to command fire support fleet operations in the air at any time, making it difficult for German Navy submarines to carry out “wolf pack” war.

From April 28 to May 6, the German Navy submarine group sank 13 transport ships in the continuous operation against the escort transport team of “ons-5”, but it lost 6 submarines and another 4 submarines were seriously damaged.

In the following month, the German submarine group also suffered serious losses in the battle against the escort transport teams “sc-129”, “hx-237”, “sc-130”, “ons-184” and “hn-239”.

As dunnitz wrote in his War Diary on May 24, “our losses have been intolerable so far in May.

” In view of the serious losses of submarines, the German Navy decided to temporarily stop the operation of submarines in the North Atlantic.

Except that some submarines with small oil storage remained in this sea area, all other submarines withdrew to the southwest sea area of the Azores.

The retreat of the German Navy in the Atlantic battlefield marked an important turning point in the struggle between the allies and Germany around the Atlantic line of communication since the outbreak of the war.

The comparison of forces between the two sides clearly shows that the allies have completely occupied the advantage in the Atlantic battlefield, mastered the air and sea control, can concentrate their escort forces on the North Atlantic traffic lines, especially in the western British Isles and the bay of Biscay, and can take the initiative to limit the range of activities of German submarines in the Atlantic.

The “tonnage war” carried out by German submarines was declared bankrupt.

Facing the turning point of the Atlantic naval battle, the German Supreme Command decided to continue to adhere to submarine warfare in an appropriate way in the Atlantic battlefield.

Even if the purpose of “tonnage war” could not be achieved, it should effectively contain the naval and air forces of the allies and support other battlefields strategically.

In order to strengthen submarine warfare as much as possible, on the one hand, the German Navy changed submarine warfare tactics and deployed submarines in the Middle Atlantic, Caribbean and Gulf of Mexico.

The original large boat screen battle in the front of two or three hundred nautical miles was changed into three or four short boat screens, which were successively launched on the route, and the aviation soldiers were responsible for searching and guiding the submarine to attack the target.

on the other handStep up the development of new submarines, improve the original submarine equipment, and try to obtain the advantage over the Allied surface ships through the breakthrough of submarine technology.

The design office of the German Navy General Command and the government equipment department concentrated their efforts to organize the rapid production of the new “Walter” submarine.

Each submarine is equipped with a retractable ventilation device, which can dive underwater all the time, making it difficult for the Allied radar locator to search the target.

Protective materials are equipped around the periscope tower to interfere with the detection of radar, and the submarine’s air defense weapons have also been strengthened.

The German Navy attempted to resume and strengthen submarine warfare on the Atlantic line of communication through a series of adjustments.

In the autumn of 1943, German submarines returned to the North Atlantic route.

According to German statistics, 60% of the acoustic homing torpedoes launched by submarines hit the target.

In September and October, the tonnage of ships sinking allies and neutral countries began to rise.

The threat of new German submarines to the Allies’ communication lines quickly attracted the attention of the allies.

For acoustic homing torpedoes, allied warships and merchant ships are equipped with “Fox” acoustic mine inducers.

The aviation forces search and guard in the form of two aircraft or small teams, forcing German submarines to dive.

The anti submarine ships are equipped with 24 barrel guns and launch deep-water bombs equipped with collision fuses, which pose a great threat to German submarines in the sea area near the transport ship.

In the third stage of the Atlantic naval battle, the Allies always maintained their advantages in anti submarine forces, technology and tactics, so that Germany’s advantages in submarine weapons and equipment and the new tactics adopted can only be effective in a short time.

They were soon restricted by the anti submarine advantages of the allies and paid a great price.

In November, Germany sank 14 allied transport ships on the North Atlantic transportation line, but it was also strongly counterattacked by the allies and lost 18 submarines.

This shows that there are new signs of negative growth in German submarine warfare, the tonnage loss of allied ships gradually decreases, and the loss of German submarines increases.

All this shows that after the turning point in favor of the allies in the Atlantic naval battle in May 1943, the German Navy’s efforts to revive the submarine war also completely failed in November 1943.

Since then, Germany’s submarine war in the Atlantic battlefield has been maintained, and the United States and Britain have fully mastered the initiative in the Atlantic battlefield.