The strongest soldier

Digging a tunnel under the eyes of the enemy is definitely a very dangerous thing, and it can only be dug in a day or two. The possibility of being exposed is very high, but Luo Zheng has no better way. He can only pray for darkness under the lamp and get through. However, Luo Zheng did not put all his hopes in digging tunnels. He agreed to Cao Xi's suggestion and looked around, then whispered: "We wait here until dark. If we run back, we will be exposed."

"That's good, it won't be long until dark." Lan Xue said in a deep voice, glanced at Cao Xi, and asked with a solemn face: "Although the place you chose is somewhat hidden, it is less than two thousand meters away from the base. , I have a question, the dark prison is underground, do you know where it is? Don’t dig too far.”

"No, the prison should be somewhere outside the base. I still need to observe for a while before I can finally confirm it. Give me some time." Cao Xi said in a low voice, with a strong look of confidence on his face.

"Why is it on the outside and not underneath the base? Isn't it better to protect the entrance to the dark prison if it is inside the base?" Lan Xue asked curiously.

"This is not contradictory." Cao Xi whispered. Seeing Lan Xue's curious face, he explained: "The entrance must be in the center of the base. It is heavily guarded. It is difficult to get through, but the dark prison cannot be under the base. , you think, how to drain the domestic water for nearly 20,000 people? It will definitely seep into the ground, and over time it will seep below 200 meters, causing the dark prison to rust, collapse, leak, etc. This is not advisable, so , the dark prison must be on the outside, but the passage is inside the base."

"It makes sense. If that's the case, the dark prison should be some distance away from the underground river and upstream. Otherwise, the domestic water in the dark prison cannot be drained out. In other words, there must be an underground river below. We just need to find the location of the water well. You can determine the approximate location of the upper reaches of the river." Luo Zheng said thoughtfully.

"You are right. Whether above or underground, domestic water must be drained out. It is impossible to dig drainage ditches here. If domestic water is allowed to pour randomly, it will change the geological structure of the base over time. We can only use underground rivers for drainage. The ground Domestic water flows underground through drainage wells, food wells are upstream, and sewage wells connect downstream, so we only need to find the locations of domestic water wells and sewage wells." Cao Xi praised.

"It makes sense. It seems that there is a high possibility that there is an underground river below, and the Dark Prison is upstream of the underground river. In this way, as long as we find the direction of the underground river, we can roughly determine the location of the Dark Prison." Lan Snow said in surprise.

"The dark prison has a drainage channel that connects to the underground river. Maybe we can infiltrate in." Luo Zheng looked at Cao Xi in surprise and asked. Seeing Cao Xi's affirmative nod, he continued to ask with a little more information: "Yes Doesn’t it mean that no matter where we dig the tunnel, as long as it leads to the underground river, we can find the drainage channel along the river, and then penetrate into the dark prison?”

"There is a problem. Everyone has a problem with swimming. They are afraid that there is no air in the underground river." Lan Xue reminded.

"No, the underground rivers under the desert are not very big, but the soil is relatively loose, the river channels are not small, the space is large, and they are living water. If there is air, it is cold." Cao Xi denied.

"Are you afraid? Our equipment is waterproof. The top priority is to dig the underground river." Luo Zheng said nonchalantly and quickly checked the base, eager to find the direction of the underground river.

"I can roughly determine the location of the underground river. Below the tall hill I just mentioned is the lower reaches of the underground river. It must be about two hundred meters deep. Have you found it? If you go further, the overall terrain will sink. If you can find it, If the terrain is lower, our digging time can be shortened a lot." Cao Xi said with certainty.

"Can I use the aerial coordinate map for you?" Luo Zheng asked in surprise.

"Okay, show me." Cao Xi agreed.

Luo Zheng quickly took out his mobile phone and called up the three-dimensional topographic map of the base. It clearly marked where there were sand dunes, where there were sand valleys, and what the altitudes were. Luo Zheng took a closer look and found that the altitude was indeed starting to decrease to one side. He couldn't help but be overjoyed and quickly handed the phone to Cao Xi.

Cao Xi took it and distinguished it carefully, not missing any details, while observing the actual terrain around him. After a while, Cao Xi pointed in the direction of the tall sand dunes in front of him with a sure look on his face and said: "Go that way, there is a valley about five kilometers away. The sand valley is covered with sea buckthorn, and there should be an underground river less than a hundred meters below."

"Five kilometers?" Luo Zheng looked at Cao Xi worriedly.

"Don't worry, the underground river is living water, and the river cave should be large and have air." Cao Xi said confidently.

"Well, let's go to the place you mentioned. It's still too close and too deep from the underground river. Excavation will take time." Luo Zheng said thoughtfully, while looking up in the direction Cao Xi said.

"Go now." Cao Xi suggested.

Luo Zheng thought for a moment and glanced at Lan Xue, who nodded knowingly and said, "Okay."

The three of them got up and looked around cautiously. After finding no danger, they quickly trotted towards their destination. Five kilometers was not far, but in order to avoid detection, the three of them circled the hills as much as possible and walked as much as possible. On top of that, we encountered a patrol on the road, so we were delayed for about ten minutes while avoiding it.

An hour later, the three of them arrived at the valley Cao Xi mentioned. Sure enough, they saw that the valley was covered with sea buckthorn. The tall ones were more than 1.5 meters tall and the short ones were about half a meter long. They were full of fruits. Luo Zheng said in surprise: " Even if there is no access to the underground river, it’s still worth it, so many sea buckthorn berries can just replenish everyone’s water and vitamins.”

"On the aerial photo you showed me, I only saw sea buckthorn trees. I didn't expect the sea buckthorn trees here to be so tall. It's great. The fact that they can grow so tall has a lot to do with the underground river below. I judge that the underground river is not far from the ground. It's more than thirty meters, and I can dig the tunnel in two hours at this depth." Cao Xi said in surprise.

"Two hours?" Luo Zheng looked at Cao Xi in surprise. Thirty meters is not a shallow place. It would take a whole night to dig with all his strength. Cao Xi actually said that it could be dug in two hours. He couldn't help but ask in surprise. : "You can't joke around on the battlefield. Are you sure you can do it in two hours?"

"No problem, don't worry." Cao Xi said confidently.

"Manual digging is not fast, do you have any ideas?" Lan Xue asked curiously.

"Of course, you will know in a moment." Cao Xi said confidently.

"Okay, it's up to you." Luo Zheng looked at the sky. It was almost dusk. The sun as big as a millstone was hanging in the west, red. The sunset glow was dense, dyeing the western sky red, and the temperature began to drop. He couldn't help but sigh. Said: "I will contact the main force immediately and ask them to come here to meet up. We will take action as soon as the team arrives."

"No need to wait, I'm starting work now." Cao Xi said confidently.