On the sea more than 300 kilometers away from Camps, the mighty and majestic American fleet slowly advanced forward. In the dark night, only the low roar of ships was heard, but no light could be seen. .

Nimitz and Hewitt are both very cautious people. The closer they get to the Rio defense circle, the more cautious they are. Of course, lighting control will not be ignored. In order to maximize navigation safety, Nimitz has also studied many plans, and specifically the action routes of the two fleets, and after consideration and consideration, different plans were designed:

The two fleets were moving south in a parallel state with the east coast of Brazil. The transport fleet was in the inner circle and the main fleet was in the outer circle, with a distance of about 200 kilometers from each other. At the same time, the main fleet was more than 200 kilometers ahead of them, which was 250 kilometers southeast of the transport fleet.

This march formation is of great intention. At present, the threat of the US fleet is mainly composed of three: first, the hidden German fleet; second, the German Air Force with Rio as the main base; third, the German wolf pack hidden underwater. These three dangers cannot be eliminated, and there must be some choice. Nimitz distinguishes according to the degree of danger, and the higher the ranking, the higher the degree of danger.

If you avoid the attacks of shore-based aviation, the farther away from the coastline, the better. However, in this way, the possibility of hitting the German fleet will increase. If you let the German fleet run into the transport fleet, Nimitz believes that the enemy can send all the main forces of the transport fleet into the seabed in just one hour, so you cannot lean too far into the deep sea.

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

It is not possible to let the main fleet and the transport fleet be mixed together. First, the speed of both sides is different, and second, the fleet is too large and it is easy to become the target of submarine attacks. It is not possible to leave too far, which is not conducive to escort.

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

His analysis is very reasonable. The German army currently uses i and iii class submarines in Brazil's waters are both 2,000 tons in the displacement, and shallow sea activities are not suitable and cannot be used. But one thing the Americans did not expect was that Crank mobilized about 30 submarines not to land on the fleet, but to restrain the main fleet of the US military.

Many people were surprised by this, and even Hinz believed that submarines should be given priority to landing fleets. Crank listed two important reasons:

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

Second, attacking the landing fleet is not very meaningful. Once the German South Atlantic Squadron eliminates Nimitz's main fleet, he can completely grasp the South Atlantic sea control. What is the landing fleet in front of an aircraft carrier? It's just a pile of scrap copper and iron!

These two reasons convinced everyone.

The brave Crank finally mobilized more than 30 submarines through the Azore Base to ambush in the waters where the US troops headed south. In order to pursue the maximum ambush effect, several submarines gave up attacks on the landing fleet two days ago and focused on moving south to build an ambush circle.

The reconnaissance aircraft that take off from Rio every day must reposition and sort out the location of the US fleet. The purpose is not to use aviation troops to attack, but to analyze the feasibility of Nimitz's road to the south and arrange ambush.

Now, this opportunity has finally come!

Nimitz is not ignorant of the risks to come, on the contrary, like all U.S. Navy generals, he attaches great importance to anti-submarines.

In this time and space, German submarines pose a fatal threat to Britain and the United States. In order to improve anti-submarine capabilities, Britain and the United States have made many strange moves and continuously strengthened their own response strategies.

The first step in the fight against the escalation was to improve the original isolated and individually launched deep-water bombs into hedgehog bombs. Although the loading volume of hedgehog bombs is not as good as that of deep-water bombs, it uses a system launch module. A single launch frame has 24 gun barrels and is tilted forward 45 degrees (so many gun barrels are leaning against each other, so it is named after the name). The hedgehog bomb launch frame is generally installed on the bow deck. During a volley, 24 hedgehog bombs are fired one after another at very short intervals, forming an elliptical barrage in the sea. Once the submarine is shrouded in the barrage, it is difficult to escape.

Generally, one set of destroyers can be installed, and two sets of ten thousand tons of treaty cruisers can be installed. In anti-submarine, two or four destroyers are usually installed. At the same time, it also has the ability to reload quickly. Hundreds of hedgehog bombs can be poured out within an hour, blowing the submarine officers and soldiers under the sea until the mental collapse.

After 1942, Britain and the United States introduced large aircraft anti-submarines. When the weather was sunny, submarines within 30 meters of the water could be discovered. The discovered submarines were usually destroyed by the bombing of hedgehog bombs thrown by the aircraft. Even if they could not be bombed and sunk in German submarines, they could force the opponent to submarine deeper and deeper. In addition to traditional visual detection, large searchlights, radars and other auxiliary observation facilities were also installed on the aircraft, making it unsafe to float and charge U-boats at night.

In order to cope with this situation where the road is one foot high and one foot high, the German army introduced innovative snorkel technology, so that the submarines can be charged without having to float and only expose the snorkel, greatly improving the survival rate of U-boats. However, the good times did not last long, and the United States' response measures were born from the use of microwave surface search radar.

This radar was produced by the United States using British magnetrons. It has a power of 50k, a pulse width of 1.3~2use. It has a working frequency of 3000mhz. The US military calls it the SG-1 radar. It can capture enemy aircraft flying low on the sea missed by low-frequency radar, and can also capture periscopes 9,000 meters away and large ships 30 kilometers away. For snorkels smaller than periscopes, it is found that the distance is about 5,000 meters. Since this distance exceeds the launch distance of the G7 torpedo, it is very threatening to the U-boat.

Experienced US radar soldiers use SG-1 radar to search the surrounding sea surface at night, find out suspicious highlights and track them, and then directly read data from a mechanical calculator. Most of the time, these highlights are real snorkels. The US military either uses hedgehog bombs to sank U-boats, or force their opponents to give up attacks and sneak into the water to achieve safety measures.

In order to deal with the terrifying radar detectives, the German army activated various radar warning aircraft, including those that capture surface ship radar signals, microwave radar signals, and aircraft radar signals (they usually have different wavelengths), but Britain and the United States also changed the frequency in time to invalidate the alarm receiver. For example, after the sg-1 radar was improved, it used a 10,000mhz frequency, which immediately destroyed the alarm system that the German army had worked hard to develop.

In 1943, the German army began to improve the material of the snorkel under Hoffman's prompt, changing the upper end of the snorkel exposed to the water to weaken the composite material that absorbs radar waves. This is a consideration of 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 distance of the SG-1 radar to about 2,500 meters (at night). In addition, after the German army activated the long-range and fast oxygen torpedo, it was enough to occupy a favorable launch position before the US military discovered the snorkel signal. This gave the German army the lead in the breaking confrontation in 1943. A large number of British and American cargo ships were sent to the seabed. In addition, the growth of the German surface fleet and the victory of the Azores base air confrontation, the best anti-submarine method used by the Allied transport fleet was to ignore the German submarine and use the direct rush method to break through hard.

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.

Sonar has always been a distinction between active and passive. For strategic considerations, the United States and Germany have taken different development paths: the US military focused on developing active sonar, increasing the exploration distance of sonar from about 2,000 meters to more than 4,000 meters, and also activated the joint exploration of dual-drives, that is, two destroyers simultaneously detect a sea area and quickly exchange information for comparison. If the difference is large, it means something is different; Germany vigorously developed passive sonar, with a unique level than the world, with a detection distance of nearly 7,000 meters. In addition, German scientists have also developed a rotating base array, changing the single beam scanning in the horizontal direction generated by mechanical rotation to multiple sonars for fan-shaped partition scanning, greatly improving the exploration efficiency.

On this basis, Germany launched an unprecedented i-class submarine, which is a real "submarine". The entire submarine highlights the underwater streamlined design and greatly reduces the deck gun (later completely cancelled at Hoffman's suggestion). The streamlined body can achieve faster navigation speeds underwater than freighter (whether victory or free wheel) underwater. On the other hand, this class submarine is equipped with a system that uses hydrogen peroxide as an oxidizer and has a primary AIP function. The latency time can be greatly enhanced, from the previous few, dozens of hours to 54 hours. When the iii-class submarine is further expanded, the complete latency time is increased to 88 hours.

At the same time, this class of submarines has also introduced all other advanced technologies, such as double-layer hulls, which have another layer outside the pressure hull. Passive sonar and other facilities are set outside the pressure hull, which improves space utilization; rotating base array sonars that can detect precise orientations and distances are used so that the submarine can launch torpedo attacks without raising a periscope; and linear guide torpedoes are also used.

Originally, the line guide torpedo developed by Germany during World War II was called "Skylark", which sounded very gentle, but after Hoffman instructed to use the line guide function based on the g9 super oxygen torpedo (spike modification), this thing turned into a murderous name Tiger Shark!

Half of the torpedoes carried on the 29 i-class submarines are tiger sharks and half are spear modifications. The two ii-class submarines led by the lead are majestic tiger sharks.

They were quietly waiting in the deep sea for their prey to hit the door...
Chapter completed!