The Entente has long noticed Germany's unlimited submarine warfare, in the North Atlantic, there have always been active German submarines, the Seawolf force from the very beginning of the scale, to now, continue to expand, more than 1000 tons, even 1500 tons of ocean-going submarines, emerge in an endless stream, even if the British and American fleets have been careful enough, sent a large number of warships to escort, but the sinking rate is not low, 10 losses once, almost an iron law, because the submarine can not be found, the German submarine is even bold, Ventured into the anchorage of the group to attack, took advantage of the chaos, attacked a few merchant ships, and sailed away.

Although the listeners resumed training with the support of Britain and the United States, the human ear, not only the range of hearing is too small, but the probability of being affected is also quite high, as long as at night, under the chaotic environment, the probability of success is very large, which makes Britain and the United States suffer a huge blow, and even cancel the original anchorage, as long as it is not the arrival of a storm, or other necessary conditions, few choose to anchor at night, even if it is traveling.

Britain and the United States are looking for a reliable way to find submarines, Britain can only extend on the basis of listeners, hoping to find better listeners from the middle, it seems to have some effect, a few gifted listeners, can reach 30% accuracy, at least 4 times higher than the 7% accuracy of ordinary listeners, which makes this group more efficient, but unfortunately there are only 3 such personnel, and it is impossible to listen for a long time, at most 6 hours of all-out efforts, you must rest.

On the contrary, the United States jumped out of the listener and chose other aspects. The excellent scientific and technological conditions and industrial base of the United States have absorbed the top technology of the United Kingdom. The level of science and technology in the United States is like entering a fast lane, and it is improving rapidly in all aspects.

Sonar is an underwater sounding device. It was originally the brainchild of the British, but the British could not continue it, but the United States saw this, went deeper, invested a huge amount of money, and achieved considerable results.

At the beginning of 1915, the United States made a certain breakthrough in the development of sonar. The United States began to install and debug sonar systems on destroyers, and the effect was slightly better than that of listening, which gave the Americans hope that sonar is a machine, as long as the reliability is guaranteed, it can continue to produce results, not like the listener, when he goes all out. The effect is okay, but it doesn't last long, and the difference in accuracy between the peak and other periods is a bit large.

The initial results have been so good. This makes the United States firm in its belief in continuing to study the level of science and technology in the United States. Much stronger than the UK, and abundant human resources. As long as you increase investment, there will definitely be gains.

Next. The United States increased investment, and gradually solved several key problems of sonar, and finally produced a practical sonar, after a little use in the United States, found that the effect was good, and put it into the North Atlantic shipping lane, the sea wolf force brought great pressure to the Entente, even if it was as strong as the United States, it was a little unbearable, let alone the United States, as soon as the primary product of sonar came out, even if it was not subjected to strict and necessary testing, to see if there were any side effects, it was installed.

In fact, the Americans' approach is very right, the strength of the submarine, the main thing is concealment, after all, for the underwater ship, the huge sea, the thick sea, is his greatest protection, with these, can be a sneak attack on the ship, a 1500-ton submarine, in the case of the maximum effect, can even sink more than 30,000 tons of battleship.

Of course, this is theoretical, the battleship cannot act alone, and it is unlikely that it will be overtaken by submarines, as for ambushes, above naval battles, the possibility is too small, submarine against battleship, the chance may be only once, and capital ships of more than 25 knots, at high speed, it is almost impossible to be attacked by submarines.

Sonar this kind of thing, is to eliminate the protection of the submarine, the current accuracy rate, stronger than the ordinary listener, but not as good as the most elite kind, but 24 hours at this point, it is very important, as long as the sonar can find the submarine, then for the submarine, it is really a catastrophe, with clear instructions, the destroyer with a depth charge projector installed, can easily sink the submarine, with the shell of the submarine and there is not much protection, mainly the sealing effect, any depth charge, explode at close range, The shock wave is enough to tear the hull of the submarine, and any loss of the hull of a ship sailing underwater must float, otherwise, it will become like a jar, filled with water, and sink to the bottom forever.

The submarine that could not be found before, the submarine became the wave, and became the most important weapon of Germany to fight the Entente, mainly displayed on the sinking of the local merchant ship, the hidden position and the sea, which was their greatest protection, with the help of sonar to find the submarine, to some extent, the entire North Atlantic, became a forbidden area for submarines.

There is no way, the German submarine is still the first generation of submarines, the pursuit is mainly a matter of size, more oil, more bomb load, in the sound processing of submarines, or the most basic stage, ordinary listeners, after training, can distinguish clearly, not to mention the sonar of technical equipment, after simple processing, it is enough to hear the action of the submarine within a range of 5 kilometers, and then, it is the time when the submarine is unlucky.

In late September 1915, the United States made a series of attempts, and found that the results were very good, although they did not choose to attack, but at least many submarines were found along the way, and this efficiency was definitely not low.

Through the introduction of the United States, Britain was also skeptical, and personally tried, after discovering the effect of sonar, immediately asked for installation, busy for several months, and finally had enough sonar, from November 2, 1915, the United States and Britain jointly carried out a fisherman operation, at least 120 destroyers and light cruisers equipped with sonar, active on the North Atlantic route, after a month of fishing, achieved excellent results, at least 107 German submarines were sunk, The role of escort is extremely obvious, from the 12th, to the end of the month, only 7 ships sank, of which 3 were silent on the reef, and had little to do with submarines.

For Britain and the United States, on the North Atlantic route, the most terrible thing is the German submarine, the German submarine can freely look for targets, a certain percentage of the sinking rate, so that the British and American merchant fleet is estimated to take 3 years, it will be replaced, not to mention the materials in it, every loss is unbearable, but now, with such an underwater eye, the German submarine is really a vegetable, any destroyer equipped with sonar and depth charges, You can deal with a submarine independently.

Britain and the United States on the North Atlantic route, after achieving results, also want to copy them in the direction of the Pacific and Indian Oceans, where submarines are also active, although not many, but also caused losses to the Entente, but the production of sonar is limited, and for the time being, it can only support the North Atlantic route.

Thanks to the difficulties, otherwise Britain and the United States arranged sonar there, but could not find submarines, which is equivalent to a waste, in the Pacific and Indian Ocean routes, the active subject is the submarine from China, which is different from the German primary submarine, these submarines have been treated, and will not choose the gasoline engine under the water, etc., the water is a diesel engine, the underwater will install a battery, the underwater is all-electric propulsion, on the propeller, fluid mechanics is also used, at least the sound wave is reduced to less than 100 decibels.

It does not reach the effect of a black hole with a murmur of the bottom of the sea like 90 decibels, and 100 decibels is a nightmare for primary sonar in this era, even if the amplitude of sonar discovery in the northwest is not high, let alone a primary product like the United States.

Surface ships are not a grade for underwater ships, underwater submarines only need to do a good job of hiding, surface ships not only have to attack, but also to discover in time, the bottom of the ocean in general nature, there is a noise of about 90 decibels, which is not found by the level of computers in later generations, let alone this era, this era has no way at all.

The continuous losses surprised Germany, the silence of a submarine, on behalf of dozens of carefully trained sailors to explain, unlike surface ships, there is no room for recovery, unless the submarine chooses to float, but those who can enter the submarine force are extremely loyal to Germany, and the underwater is different from the above, resulting in the boredom under the water is far from being compared with the surface.

The Germans could not accept the loss of a dozen or so ships, more than 100 ships, and almost tens of thousands of officers and men, and even wanted to inquire about China. Through the investigation, China finally determined that the Americans used sonar, that is, sonar appeared in the world faster than in history, and was used in the war.

For them, the feast of submarines is gone, risking their lives to attack the fleet escorted by warships, and they do not even dare to approach, and the German side has also changed the method of submarine attack, and when the ship is discovered, it is necessary to shut down the aircraft to prevent being discovered, and before attacking, it will find out whether the other side has an escort, and if it is found that there is no escort, it will attack.

In this way, the losses of submarines have been greatly reduced, and the results of the attack have also been greatly reduced, but the destructive power of the British and American fleets is almost equal to zero, and there is no way, to ensure safety and pursue results, this is impossible. (To be continued.) )