Underwater visibility still hasn't improved, but Ye Fei has also found his own way, that is, ultrasound positioning.

It is well known that bats and dolphins are masters of echolocation using ultrasound, and there is precisely an echolocation system on the combat armor that is used in complete darkness!

Under turbid water, all sorts of optical systems do not work effectively, but the use of echolocation systems is just right!

Although echolocation can only determine the general situation, and it is an all-black and white outline pattern, which is not at all like what the human eye usually sees, it is still a hundred times stronger than a black eye.

After the first generation of sound wave detection device emits a sound wave, it must wait for all the echoes to be received before the second sound wave can be emitted, otherwise the detection device will be wrong due to the interference between sound waves, and even cause detection failure.

At present, the detection device equipped with the detection device has strengthened the applicability of the third generation of products, the emission frequency of ultrasonic waves is about 50 times per second, and the frequency of each sound wave has a slight change, just like the deliberate change of tone when people speak, the receiving device can judge the time of echo emission according to the specific sound wave frequency, and will not confuse any two similar sound waves.

Due to the increase in frequency, the ultrasonic detection device can obtain more than 40 images per second, and continuous playback on the mask can obtain uninterrupted environmental images.

However, the propagation speed of sound is limited, and the reaction speed of the detection device with sound wave as the carrier is much slower than that of other means, and the time difference between the first round of echo and the last round of echo of the same sound wave sometimes produces more than ten seconds, so the farther the distance of the detection target. The lower the accuracy of the ultrasonic detection device, the more effective the application distance of the ultrasonic detection device is usually limited to within a kilometer.

The speed of sound propagation in the thin air of the bone mound will be much lower than normal, but the speed of sound in the water is much higher, and the detection range of kilometers is enough.

Ye Fei combined the digital model of the bone mound and the surrounding terrain detected by ultrasound, and reluctantly judged his current position, and used this as the basis for judging the direction of progress, and continued to advance towards the passage.

A few minutes later, a bottomless pure black hole appeared on the screen formed by the combination of ultrasounds, and Ye Fei pulled the flint to the vicinity of the hole.

Ye Fei grabbed a soft vine root with the help of a tactical lamp. Shook it a few times vigorously. Like a snake that has pulled off its bones, the root of the cabbage lies on its stomach and drifts with the current: "There is no undercurrent at all, and the flood should have flowed in completely." "Let go of your hand, and the vine roots ripple lightly.

The density of vine roots seems to be close to that of water, and they remain suspended in water for a long time. That is, it does not sink or rise.

"That's good news." Flint said. "What are we waiting for?"

The torrent when the "Dong Hong" first appeared has completely disappeared. That is, the two people entering the passage will not be disturbed by the rapids.

"Gone." Ye Fei pulled the flint into the hole.

The diameter of the hole was about seven meters, and he could see the surrounding situation with just the light of the tactical light, but Ye Fei did not turn off the ultrasonic detection system. Instead, the tactical lights were turned off.

Whereas light cannot reach far in still turbid water, ultrasound can provide images from a distance, and the light can easily reveal its position.

If the Outer Bone Men were ambushed in this newly formed waterway, Ye Fei, who used ultrasonic pathfinding, would definitely be able to spot them in advance. On the other hand, if the tactical light is turned on, it is 100% Ye Fei who is discovered.

The two of them walked along the passage and rushed out of the water not long after.

The fork in the road leading from the farm to the three hollows was a little higher, Ye Fei originally thought that he could swim directly to the other two hollows, but he didn't expect to have to go ashore and walk a few steps halfway.

I don't know if it was because of the erosion of the water, after entering the bone mound, the ubiquitous glimmer on the rock wall was all gone, and the water surface was pitch black and the five fingers could not be seen.

Ye Fei quietly poked his head out of the water, and the invisible ultrasonic wave swept over, and he didn't find any moving objects: "Safe!" ”

Ye Fei and Flint stepped onto the slippery rock and quickly headed towards the three-way intersection.

The further they went, the steeper the passage became, and the distance of more than 100 meters to the back of the road almost became a vertical shaft, and the two had to fly into the air with the help of Ye Fei's thrusters to reach the three-way intersection.

Flying to the fork in the road, Ye Fei found that the tilt angle of the passage in the direction of the farm was not large, but when he reached the corner, it directly turned into a vertical sharp turn, and this place was simply three shafts side by side, which was more accurate than Mitsui.

The passage that Ye Fei came out of was only seven meters, and the hole below was marked by him as No. 7, the shaft in the middle was nearly twenty meters wide, and the hole below became No. 20, and the last one was only about four meters, which was naturally No. 4.

"Boss, there's a signal forty meters above!" Flint suddenly noticed a stationary green dot on the radar, "Quick, he's not in the right situation!" ”

If the speed of the green dot is incorrect, it means that there is something wrong with the heart represented by the green dot - the green dot will cause the radar positioning to fail, so the stop jump is represented by the green dot stopping flashing.

The ultrasonic detection device had long determined that there were no moving objects nearby, and the situation was urgent, Ye Fei could no longer care about the hidden position, turned on the tactical light to illuminate the dark passage, and jumped to the position of the signal in a few steps under the leadership of the flint.

In the bright pillar of light, the three long legs of the giant insect were stuck in the passage like a beam, and the second leg of the long leg was bent, just in the direction of the farm.

The shortest section of the long leg was only a little more than a meter long, and the tip split into a pair like scissors, and when the pillar of light of the tactical lamp stopped at the tip of the long leg, the pupils of both of them shrank at the same time.

A warrior had been pierced in half by the tip of his leg and was hanging limply on it, motionless.

Ye Fei lifted the mask, his heart seemed to be clenched by an invisible big hand, almost unable to beat, he jumped up to support the warrior, and quickly checked the warrior's situation, but the warrior's brain wave was only left in a straight line.

If there is still a trace of consciousness, the head can be frozen, but the brain waves have completely disappeared. It means that the brain has completely died, and no matter how advanced medical technology is, it cannot be saved.

"I'm sorry we're late." The corners of Flint Shi's eyes were sour, "Bastard, I haven't eaten enough walnuts you sent, you are dead, what will Lao Tzu eat?" Your father and mother will come to the army again, how can I see them......"

The sacrificed fighters turned out to be two detachments of walnuts.

The commando team has a small number of personnel, and there are only more than 20 people in a squadron. They know each other very well. Walnuts always give walnuts to everyone. The popularity is second to none in the whole team.

Flint and him are in a squadron, the two usually look up and don't look down, and the thought that from now on the comrade-in-arms who grabs a handful of walnuts everywhere with a simple smile will never appear again, Flint's heart hurts as if it is torn in half alive.

"Even if we come early, it's useless." Ye Feiqiang held back the tears in his eyes. "Trauma to the abdomen was not the reason for his sacrifice. The massive rupture of cerebral blood vessels was the reason for his sacrifice. ”

Thinking of Walnut's expression every time he saw him, he was honest and slightly nervous. The bits and pieces of the past five years flashed in front of his eyes like a movie.

For the first time, Ye Fei hated his memory for being so good.

It took a very short time for the out-of-control flint to regain control of his emotions: "Was that impact? ”

Ye Fei nodded: "It would be nice if I just froze him up at that time." ”

Flint bit his lip: "Boss, can you take him with you?" I'm in charge of taking him with me, and he's gone. You can't leave him here, you can't even go home. "Although I haven't encountered high-intensity battles since entering the bone mound, it doesn't mean that it will be smooth in the future, bringing the remains of walnuts will occupy a person's combat power.

Reason told Ye Fei that he couldn't do this, but he didn't want to think about it and nodded: "If you don't say it, I will do it too." ”

Flint choked gratefully, almost speechless: "Give me a little time!" He couldn't bear to pick the walnut directly, took out his saber and slashed it at the back joint of the long leg like crazy, and slashed more than a dozen in a row, and finally cut off the worm's leg with the knife.

Placing the walnut flat on the ground, the flint carefully pulled out the worm leg that pierced the abdominal cavity, and the sealing function of the armor was automatically activated, and the front and rear wounds were closed at the same time, and the little blood stains on the wound were so dazzling.

The flint activated the remote control function of the armor, and Walnut stood up under the drive of the armor as if it came to life, but on the communication screen, Walnut's head hung weakly in the helmet, and his eyes were closed and his face was pale.

He returned Ye Fei's gun, took off the walnut gun and held it in his hand: "Brother, I will definitely take you home." ”

Ye Fei gritted his teeth and patted the flint's shoulder: "Let's go, it's not time to be sad yet." "Soldiers on the battlefield do not have the right to cry, and can only indulge suppressed emotions at the funeral of their comrades.

Walnut's sacrifice seemed to press a mountain on Ye Fei's heart, he was originally optimistic that everyone would be safe and sound, but the reality gave him a heavy blow.

Ye Fei hoped that no one else would be sacrificed, but he knew very well that this was just wishful thinking.

There are no immortals in war, and when a soldier goes to the battlefield, who doesn't tie his head to his belt and die to survive? Whether or not you can get off the battlefield alive or not, there is nothing but luck.

Ye Fei's soldiers have not sacrificed, when the Yangtze River was wrecked in the Giant Star, the whole ship was reduced by 1,000 people, and most of them couldn't even find their bodies.

He knew very well that the commandos would die sooner or later, and he had long been mentally prepared to pay heavy casualties in the battle, but when everything really came, it was so sudden, so sudden that he was completely unprepared.

The two of them took the remains of walnuts into the passage connecting the No. 20 hollow, and only found the water surface after descending nearly a hundred meters, but surprisingly there was a passage near the water surface that did not know where the road leads, Ye Fei checked the bone mound model and knew that the passage led to the No. 4 hollow.

It turns out that the two hollows are connected by a secret passage.

Ye Fei decided to take a look at the hole first, and then the two dived into the water again, there was no problem with the propulsion device on the walnut armor, and under the remote control of the flint, the walnut pulled him to follow closely behind Ye Fei and dived underwater.

The sneak took much longer than expected, about ten minutes before entering the cavity and slowly coming to the surface.

However, the situation was always so unexpected, and the surrounding cliffs gradually closed as they ascended, and when the water surface was discovered, only a narrow surface of water was only three or five meters high from the top of the cave.

The terrain of this hollow is relatively low, and it is a structure with a wide bottom and a narrow top. Typical pot-bellied small mouths. A large amount of water entered and almost filled the entire space, leaving only a little space above the hollow.

Ye Fei originally had the intention of being more careful, and when he didn't want to get close to the water, he suddenly found that there were continuous flashes of light on the water.

It's gunfire!

He immediately judged the origin of the flash: "Flint, accelerate, there are our people!" ”

"Roger!" The always lively flint was so heavy that he didn't want to speak, and he sped out of the water at a sharp acceleration.

The space on the water is roughly an oval about 100 meters long, surrounded by rock walls, and only one side has a flat land of more than 100 square meters. But now it's just flat land by the water's edge.

The edge of the stone platform happens to be a passage leading to nowhere. A large number of Exoskeletons were pouring out of the passage, and the three warriors cooperated with each other to shoot continuously, and at least hundreds of Exoskeletons fell at the entrance of the passage, and the enemies in the cave kept pushing away the corpses of the Exoskeletons blocking the entrance of the cave and rushed out. The corpses of the Exoskeleton are accumulating more and more. It actually fell into the water with a bang.

"Help!" Ye Fei immediately flew over. The rifle in his hand fired accurately, so close that almost every shot hit the skeletal man's head with unerring accuracy—though it wasn't a sniper rifle. But Ye Fei is still accustomed to taking away the enemy's life with accurate shots.

The flint held on to the trigger as if to vent the anger in his heart, and a string of bullets smashed near the hole, and the sound of sparks and ricochets was endless.

"It's the captain!" The three warriors only found out about the arrival of reinforcements when Ye Fei rushed out of the water, and they immediately became excited, and threw a few grenades into the hole in succession, and the stubborn outer bone man finally retreated.

"Captain!" As soon as Ye Fei landed, three soldiers surrounded him, and the leader was the second captain of the code militia

When the militia first joined the army, his training performance was the first in the company, and the company commander was so angry that he gave him the nickname of the militia, which means that his quality was not as good as that of the militia. The militia, stimulated, was so angry that they actually entered the selection list of the commandos after the training of recruits. Since then, the code name Militia has followed him.

The militia and the two soldiers saw the flint and the walnut with stiff movements, and the expressions of the three people immediately froze on their faces.

The immobile spot of light on the radar is the best explanation.

"Well, now is not the time to talk about that." Ye Fei stopped the soldiers' inquiry, "Only the three of you?" ”

The entrance area is large, and there should be more water coming in, and the warriors who rushed here should also be the most. Especially the structure with a big belly and a small mouth, as long as the soldiers float to the surface, they can gather together, and the conditions for gathering people are countless times better than the hollow like the underground lake just now, how can there be only three people?

The militia explained: "The captain took the others to check on the other two hollows, leaving a few of us here to see if we could wait for the other lost comrades." ”

The black bear is fine!

Ye Fei quietly breathed a sigh of relief: "How many people did he take away?" "People have distant relatives, and his biggest concern is naturally the two old brothers black bear and veterinarian.

"Ten."

"So much?" Ye Fei felt that the number of warriors rushing into here would be relatively large, but he never expected that there would be ten.

Together with the black bear himself and the three fighters in front of him, a total of fifteen commandos were gathered here.

You must know that there are only twenty-two people in the entire No. 1 Squadron of Lu Dao plus the squadron leader, plus the black bear, the veterinarian and Ye Fei, there are only twenty-five people in total.

The ten people taken away by the black bear, plus the eleven black bears themselves, counting the three soldiers left behind in front of them and Ye Fei's flint walnut, plus Tan Dong, the third prince and the praying mantis who stayed in the No. 7 hollow, there are only four fighters left who are still missing!

All four of them are likely to be in Hollow Four.

"Captain, didn't you meet the captain?" The militia couldn't help but ask.

Ye Fei shook his head: "The black bear must have gone to the No. 4 Hollow from the passage halfway through, so he didn't find the walnut ......" I don't know if Tan Dong and the others didn't wait for the other fighters.

"So what now? The three of us have been waiting here for a long time, and there should be no one. The militia pointed to the passage that didn't know where the road leads, "Counting the wave just now, they have all repelled three waves of outer skeletons." ”

Ye Fei thought for a while and said, "Militiaman, you sent someone back to the No. 7 Hollow with the flint, his thruster is broken." Flint, after you find Tan Dong, let them all take them all to Hollow No. 4 to join me, Walnut...... Leave it to me. ”

"Leave it to me, I'm his captain." The militia took the initiative to take over the command of Walnut Armor and sent a soldier to return to Hollow Seven with him, and the two did not dare to delay and set off immediately.

It's not a good idea to send the walnut with the thruster damaged back, but only by sending the flint back can you find Tan Dong and the others as quickly as possible.

Ye Fei was ready to take the others and rush directly to the No. 4 Hollow.

In case there were still soldiers stranded here and did not come up, Ye Fei carved a few words on the rock wall by the clearing before leaving, explaining his whereabouts.

Chinese characters are notoriously difficult to learn, even if they are also humans, there are countless people who have been stumped by Chinese characters from ancient times to the present, and no matter how powerful the outer bone people are, it is impossible to understand human characters, and there is absolutely no possibility of revealing their whereabouts.

The engraving was delayed for a while, and the group quickly dived underwater and went straight to the No. 4 hollow.

"Militia, did you see Staff Officer Ren?" Ye Fei asked suddenly.

"Nope." The militia, who dived side by side with Walnut, replied in the affirmative.

Ye Fei couldn't help but feel a trace of worry in his heart, I don't know what the situation of the veterinarian is in the Dao Dao, after all, he has been away from the commando team for many years, and his physical strength cannot be compared with the soldiers who have been trained all year round.

One fighter had already been sacrificed, and he now only hoped that the veterinarian and three other warriors whose whereabouts were unharmed. (To be continued......)

PS: The subscription has dropped to four hundred ...... again Is this a reminder that I've been writing badly lately?