Lu Su shook his eyebrows and said in a deep voice: "Refining nitrate is not a difficult task, Master Jia and I both know the truth. Nitrate refining needs to go through three steps: nitrate making, nitrate grinding, and nitrate grinding. Let's start with nitrate, which is to extract this unique flammable ingredient from the soil. When I was an official in the Yuan Shu Department, I asked someone to do this, and it was extremely simple. Just get some more big iron pots, and dig some soil with high nitrate content and good texture from the mountains. A long time ago, we didn't know that some mountains or plains contained more nitrate in the soil. It's just to get some dirt casually, and then it will take a lot of effort but not much to refine. Later, it was discovered that it was best to use the soil in the kitchen, because of the fact that the nitrate also precipitated a lot when cooking and cooking. Later, I found that the nitrate content in the soil in some areas was relatively high......"

"Where's the nearest place?" Pang Tong suddenly interrupted.

"In Yi County." Lu Su replied. Yi County is the area east of Chencang County, and Pang Tong's own territory.

Pang Tong nodded with a smile and said, "You continue." ”

Lu Su made a pouring motion with one hand and said, "After we put the soil into the iron pot, we keep adding water to boil it, and after a day or two, a layer of white nitrate will form on the edge of the iron pot. Then it's time to grind the nitrate. Because the nitrate particles that have just been boiled out are very large. We need to put the boiled nitrate in the grinding trough to crush, manpower, ox power grinding wheel is more laborious, I was in the city at that time very developed water power, water wheel grinding nitrate twice the result with half the effort. After this step, the nitrate crushed pellets we mill cannot be used directly. The nitrate grains must be ground into a finer and smaller powder. That's it. ”

Pang Tong applauded: "The ancients ...... It's a good idea, and it took a lot of discovery and research to invent this kind of thing. "He wanted to say that the ancients had such ideas." Is sulfur any good? ”

Lu Su said: "This is a more convenient thing, it is more convenient than refining nitrate, and the output of our territory is high." ”

Pang Tong raised his hand to call him closer, and said something about it in his ear, and Lu Su felt that it was not difficult after hearing it, so he said: "I will be able to return to my life within twenty days." ”

Ma Teng's army went out of the city to challenge for two consecutive days, but Pang Tong ordered not to fight.

Ma Teng's eldest son, Ma Chao, couldn't bear it, and took 5,000 horsemen to take advantage of the night to plan to attack Pang Tongjun's Dazhai. In the middle of the night, the night under the moon is thick, and the insects are chirping all over the ground. The weather is cold.

Ma Chaojun rode 5,000 horses, everyone with grass, horseshoe wraps, and horses' mouths. They took advantage of the cover of twilight and approached the northern fence of Pang Tongjun's Dazhai. Pang Tongjun dug a deep ditch outside Dazhai and could not get close. They took out saltpeter and rubbed it and lit kerosene torches. In an instant, the fire on the back side was like a burning plain, and the frightened patrol exclaimed, "Enemy soldiers! Enemy soldiers! ”

Ma Chao and the others threw the torch in their hands and smashed it on the camp tent. The hundreds of tents that leaned against the fence were all on fire. The soldiers in the tent hurried out. The flames are blazing. Fortunately, there was no wind that night, otherwise the camps that were close to each other would have been implicated. Pang Tong was sleeping deeply, listening to the sound of drums, and immediately rode from the couch, his eyes that were still squinting just now were wide, and a few bloodshots were lying in the whites of his eyes. He went out of the house wearing armor and holding a seven-star sword, and learned about it after asking the soldiers who passed by. At this time, Lu Bu had already led the cavalry out of the village. Ma Chao was young and arrogant, and when he saw Lu Bu's cavalry approaching, he actually ordered a charge. The two armies collided on the periphery of Pangtong Dazhai.

Lu Bu shouted: "Xiliang thief, obediently suffer death!" ”

I only heard the enemy ride and said loudly: "I am Ma Chao, the general of Xiliang!" ”

Lu Bu applauded in his heart: "I heard that Xiliang people have been boasting about his martial arts, I have always wanted to fight in person, but you sent it to the door yourself!" ”

The two armies were fighting in the dark night, Lu Bu looked for the sound just now, and then the fire in the south was reflected, and he saw that a general was also galloping towards him, it was Ma Chao who was holding a spear.

"Dog thief, hurt my brother!"

"Pang Tong has already died under my gun, you gang pretending to be ghosts!"

Lu Bu gritted his teeth. The two horses intersected, Lu Bu swept away with a halberd, and Ma Chao blocked it. The two rushed back and forth to kill more than ten together, Lu Bu became more and more brave the more he fought, Ma Chao saw that his martial arts were outstanding, and knew that he was not an opponent, and after intersecting again, he picked up his gun and fled. Lu Bu chased for a while, but was blocked by the Xiliang cavalry, and he fought hard for a while, stabbing down dozens of horsemen. Ma Mengqi in the dark night had already run away. At this time, more and more cavalry of the Pang Tong Army continued to pour out from Dazhai, and it had become a trend of encirclement and killing. The Xiliang cavalry had no choice but to flee, and they were also chased and killed for a while, and a few fled back. Some people accidentally ran into the deep pits dug by the Pang Tong army to cope with the iron chariot army, and fell and broke their flesh.

Looking at the sneak attacker who fled in embarrassment, Lu Bu swiped the liquid on the halberd.

After a period of time, Ma Tengjun did not go out of the city to challenge again. It seems that both sides are very cautious about the decisive battle that may trigger a change in the ownership of Yongzhou. Lu Su had been gone for ten days, and I didn't know how he was running around. Pang Tongyi asked the spies to actively explore the surrounding situation. Ma Teng didn't seem to want to go out of the city, and he kept to himself, and occasionally spies came out of the city to take a look. However, there was a piece of news that made Pang Tong a little worried. Liu Yan's army of 100,000 left Tangping Pass and marched boldly and recklessly on the territory of the alliance. Obviously, this has been approved by Ma Teng, or the two parties have a plan to jointly defeat Pang Tong. According to their route, the target is directly aimed at Chencang County.

Inside the Pang Tong tent, everyone's faces seemed to be covered with a layer of dark clouds. Jia Xu arched his hand and said, "I might as well withdraw the troops first." If Liu Yan's army attacks Chencang County, our army's grain road will be cut off, and there will be a big mess. ”

Lu Budao: "Indeed. If we feint to attack Chencang, and a large group of men and horses come here, and attack Ma Teng's army back and forth, we will be defeated. ”

Pang Tong shook his head, and everyone's hearts sank when they saw his statement. He said: "Don't worry too much, our grain and grass are enough for two months, and we don't have to worry about cutting off the main grain route, and Anding County in the north can support ...... for a while."

Jia Xu planned to say: "Forgive the official for bluntly saying that if Chen Cang is breached, it is equivalent to cutting off the back road of our army, I am afraid that the soldiers will be in turmoil, and the momentum is even more insufficient, why fight for a long time?" ”

Pang Tong was not afraid of this, and chuckled: "Hugh wants to underestimate Zang Ba, and the mountain people in the city are very powerful. ”

Zhao Yun said: "The last general looks at the mountain people as if they are reckless, and there is no organization and discipline at all, and it is estimated that it will be difficult to become an effective combat force in combat. ”

Pang Tong nodded and said, "I agree with you to see this opinion. He seemed to have a way out of what he had just said, Zhao Yun frowned and waited.

Pang Tong continued: "But I'm not talking about their superficial combat level, after all, there are not many of them, and after some tossing, there are less than 5,000 decent people who can be called soldiers. But what they have is the anger that hates Liu Yan more than us, and this anger buries them in the mood of death, and this mood is the best killing intent. Moreover, the mountain people have their own culture. The medical skills of the Wasai people are very high. When he said this, Dian Wei kept nodding in agreement. As long as it is applied to the treatment of wounded soldiers, the soldiers can recover quickly, so that the defenders will not be weakened. ”

Lu Bu proposed: "It's better to let Sheng Yuan lead the trapped camp back, raid the enemy's rear and disrupt his position, and Zang Ba will lead his troops out of the city again, and he will definitely be able to break the enemy." ”

Zhao Yunzheng said: "The trapped camp is a huge guard force, how can you leave?" ”

Lu Bu sighed, as if he thought that this was more important than anything else, so he no longer insisted. Pang Tong touched his chin with one hand, and said thoughtfully: "Judging from the situation reported by the spies, Liu Yan will arrive in Chen Cang for at least ten days. And most of them are infantry, and they are not much faster. No problem. ”

"Okay?"

Lu Bu repeated his words.

Pang Tong said with a smile: "If my plan succeeds, it can be done, but if it doesn't work, there is only a matter of planning for defense." ”

Jia Xu and the others frowned. Jia Xu arched his hand and said: "Although the lower officials know that there are many people who are resourceful, if they don't tell the plan, I'm afraid there will be omissions." After all, it is about the names of more than 100,000 people in our army and the safety of the people. Please also tell me the truth, and we will make suggestions together. ”

"Don't worry about it, it's not that I don't believe you, it's just that what I'm doing now, you will have doubts. Why don't I do it and explain your doubts directly. ”

Everyone looked at each other and asked no more.

Ten days later, Lu Su did not come back, and Pang Tong began to be a little worried. But three days later. In a long line, about twenty carriages came from the east, and the convoy began to enter Dazhai under the gloomy sky. The 1,000 cavalry escorting the convoy were already nervously watching the situation around them, as if they were carrying a priceless treasure. Of course, that's what Lu Su told them: "This is the key to the victory of the Pang Tong Army, and we have a great responsibility!" ”

But the problem is that this is just Lu Su's own rhetoric that he has thought of in order to boost morale. In fact, what Pang Tong wants these things for, even he doesn't know. Pang Tong walked out of the tent and went to inspect it in person. Lu Su was praised and ordered to reward those who have made meritorious deeds. This made Lu Bu, Zhao Yun, Xu Huang and other fierce generals who had been staying in the camp and had nothing to do a little unhappy, and they wanted to go on the expedition. But he asked this civilian official to go out on errands, and when he came back, he only brought back some goods that looked like a military posture, but he could still get a reward.