Chapter 982 Nimitz's Counterattack (15)

On the sea surface more than 300 kilometers away from Campos, the mighty and majestic US fleet was slowly moving forward. In the pitch-black night, only the low roar of the ship could be heard, but no light could be seen.

Nimitz and Hewitt were both very cautious people. The closer they were to the Rio defense circle, the more cautious they were. Of course, they would not ignore things like light control. In order to maximize navigation safety, Nimitz also studied many plans. Specifically, as for the action routes of the two fleets, different plans were designed after much consideration and consideration:

The two fleets as a whole moved southward in a parallel manner to the east coast of Brazil. The transport fleet was in the inner circle and the main fleet was in the outer circle. They were about 200 kilometers apart from each other. At the same time, the main fleet advanced more than 200 kilometers as a whole - 250 kilometers southeast of the transport fleet.

This marching formation was very intentional. At present, the threats to the US fleet mainly consisted of three factors: first, the hidden German fleet; second, the German Air Force based in Rio; third, the German wolf pack hidden underwater. It is impossible to eliminate all these three dangers, and some trade-offs must be made. Nimitz distinguished them according to the degree of danger, and the higher the ranking, the higher the degree of danger.

If you want to avoid the attack of shore-based aviation, the farther away from the coastline, the better, but in this way, the possibility of encountering the German fleet will increase. If the German fleet encounters the transport fleet, Nimitz believes that the enemy can send the main force of the transport fleet to the bottom of the sea in just one hour, so it cannot be too deep in the sea.

Nimitz also believes that German submarines that can operate in the Brazilian waters should all be large submarines-otherwise it is difficult to have a long range. The closer to the coastline, the shallower the depth of the sea, the easier it is to find the traces of enemy submarines, and it is much easier to anti-submarine, so it should be as close to the coastline as possible, but not too close, otherwise it will become the target of shore-based aviation

It is not good to mix the main fleet and the transport fleet together. First, the speeds of the two sides are different, and second, the fleet is too large and easy to become the target of submarine attack. It is not good to leave too far, which is not conducive to escort.

After considering various factors and weighing the pros and cons, Nimitz chose this formation - he believed that no plan or tactic was perfect, and the key was to minimize the danger.

His analysis made sense. The displacement of the XXI and XXIII class submarines currently used by the German army in the Brazilian waters was 2,000 tons, and shallow water activities were not suitable and could not be carried out. But there was one thing that the Americans did not expect. The goal of Krank's mobilization of 30 submarines was not to land the fleet, but to restrain the main fleet of the US military.

Many people were surprised by this, and even Hintz believed that submarines should give priority to the landing fleet. Krank listed two important reasons:

First, compared with the main fleet, the anti-submarine awareness and anti-submarine strength of the US landing fleet must be stronger;

Second, attacking the landing fleet did not make much sense. Once the German South Atlantic Squadron destroyed Nimitz's main fleet, it could completely control the sea power in the South Atlantic. What was that landing fleet in front of an aircraft carrier? It was just a pile of scrap copper and iron!

These two reasons convinced everyone.

The skilled and daring Crank eventually mobilized more than 30 submarines through the Azores base to ambush in the sea area where the US military was heading south. In order to achieve the maximum ambush effect, several submarines gave up attacking the landing fleet two days ago and only focused on building an ambush circle southward.

Every day, the reconnaissance planes taking off from Rio had to reposition and sort out the position of the US fleet - the purpose was not to use aviation to attack, but to analyze the feasibility of Nimitz's southward route and arrange an ambush.

Now, this opportunity has finally come!

Nimitz was not completely unaware of the upcoming risks. On the contrary, like all US naval generals, he attached great importance to anti-submarine warfare.

In this time and space, German submarines posed a deadly threat to Britain and the United States. In order to improve their anti-submarine capabilities, Britain and the United States have come up with a series of strange tricks and continuously strengthened their own response strategies.

The first step in the escalation of confrontation was for Britain and the United States to improve the original isolated and individually launched depth charges into hedgehog bombs. Although the hedgehog bomb has less charge than a depth charge, it uses a system launch module. A single launcher has 24 gun barrels, tilted forward 45 degrees (so many gun barrels close together look like hedgehog thorns, hence the name). The hedgehog bomb launcher is usually installed on the bow deck. When firing in salvo, 24 hedgehog bombs are fired in a short interval, forming an elliptical barrage in the sea. Once the submarine is shrouded in the barrage, it is difficult to escape.

A general destroyer can be installed with one set, and a 10,000-ton treaty cruiser can be installed with two sets. When anti-submarine, usually 2 or 4 destroyers are in a group. At the same time, it also has the ability to reload quickly. Hundreds of hedgehog bombs can be poured in an hour, bombing the submarine officers and soldiers under the sea until they have a mental breakdown.

After 1942, Britain and the United States introduced large aircraft anti-submarine warfare. When the weather is fine, submarines within 30 meters below the surface can be discovered. The discovered submarines are usually destroyed by the hedgehog bombs dropped by the aircraft. Even if the German submarines cannot be sunk, they can force the opponent to dive deeper and deeper. In addition to traditional visual detection, large searchlights, radars and other auxiliary observation facilities were installed on the aircraft, making it unsafe for U-boats to surface and charge at night.

In order to deal with this situation, the German army introduced innovative snorkel technology, which allowed submarines to charge without surfacing and only exposed the snorkel, greatly improving the survival rate of U-boats. But the good times did not last long, and the United States' countermeasures - microwave surface search radar was born.

This radar was produced by the United States using British magnetrons. It has a power of 50KW, a pulse width of 1.3 to 2usec., and an operating frequency of 3000MHz. The US military calls it the SG-1 radar. It can capture enemy aircraft flying low on the sea surface that are missed by low-frequency radars, as well as periscopes 9,000 meters away and large ships 30 kilometers away. For snorkels smaller than periscopes, the detection distance is about 5,000 meters or more. Since this distance exceeds the launch distance of G7 torpedoes, it is very threatening to U-boats.

Experienced US radar soldiers use SG-1 radars to search the surrounding sea surface in circles at night, track suspicious bright spots after detection, and then read data directly from a mechanical calculator. Most of the time, these bright spots are real snorkels. The US military either uses hedgehog bombs to sink U-boats, or forces opponents to give up attacks and dive underwater to achieve escort safety measures.

In order to deal with the terrible radar detectives, the German army activated various radar warning aircraft - some captured surface ship radar signals, some captured microwave radar signals, and some captured aircraft radar signals (they usually have different wavelengths), but the British and Americans would also change the frequency in time to make the warning receiver ineffective. For example, the SG-1 radar was improved to use a frequency of 10000MHz, which immediately abolished the warning system that the German army had painstakingly developed.

In 1943, the German army began to improve the material of the snorkel under the suggestion of Hoffman, and changed the upper end of the snorkel exposed to the water to a composite material that can weaken and absorb radar waves - this is a consideration of killing two birds with one stone. These materials and coatings can also be used to improve the stealth performance of aircraft and vehicles in the future.

This measure was very effective. The special coating developed by German scientists successfully compressed the detection range of the SG-1 radar to about 2,500 meters (at night). In addition, after the German army activated the oxygen torpedo with a long range and high speed, it was enough to occupy a favorable launch position for attack before the US military discovered the snorkel signal. This gave the German army an advantage in the 1943 confrontation. A large number of British and American cargo ships were sent to the bottom of the sea. In addition, the growth of the German surface fleet and the victory of the Azores base aviation confrontation finally forced the Allied transport fleet to adopt the best anti-submarine method, which was to ignore the German submarines and just use the direct rush method to force them.

By the end of 1943, the confrontation situation escalated again. The United States made key improvements in two areas: one was to develop advanced active sonar; the other was to improve and increase the power of microwave search radar.

There has always been a distinction between active and passive sonar. Due to different strategic considerations, the United States and Germany have taken different development paths: the US military focused on the development of active sonar, increasing the exploration distance of sonar from about 2,000 meters to more than 4,000 meters, and also enabled dual-drive joint exploration - that is, two destroyers simultaneously detect a sea area and quickly exchange information for comparison. If the difference is large, it means that there is something wrong; Germany vigorously develops passive sonar, which is unique in the world, with a detection distance of nearly 7,000 meters. In addition, German scientists have also developed a rotating array, changing the original single sonar to produce a single beam scan in the horizontal direction through mechanical rotation into multiple sonars for sector-shaped partition scanning, which greatly improves the exploration efficiency.

On this basis, Germany launched the unprecedented XXI-class submarine, which is a real "submarine". The entire submarine highlights the underwater streamlined design, greatly reduces the deck guns (later completely cancelled at the suggestion of Hoffman), and the streamlined body can achieve a faster sailing speed underwater than a cargo ship (whether a Victory or a Liberty). On the other hand, this class of submarines is equipped with a system that uses hydrogen peroxide as an oxidant and has a primary primitive AIP function, which greatly enhances the lurking time from several or more hours to 54 hours. By the time of the XXIII class submarine, the displacement has been further expanded, and the full lurking time has been increased to 88 hours.

At the same time, this class of submarines has also introduced all other advanced technologies, such as a double hull, with another layer outside the pressure hull, and passive sonar and other facilities are set outside the pressure hull to improve space utilization; a rotating array sonar that can detect precise azimuth and distance is used, so that the submarine can launch a torpedo attack without raising the periscope; and wire-guided torpedoes are also used.

Originally, the wire-guided torpedo developed by Germany in World War II was called "Skylark", which sounds very gentle, but after Hoffman instructed to use the wire-guided function on the basis of the G9 Super Oxygen Torpedo (Lance Modified), this thing became a murderous name-Tiger Shark!

Half of the torpedoes carried by the 29 XXI-class submarines are Tiger Sharks and the other half are Lance-modified. The two leading XXIII-class submarines are all equipped with majestic Tiger Sharks.

They are quietly waiting for their prey to come knocking on the door in the deep sea...

ps: There will be another update at night...