The story of the ancients conveying information:

I heard from the old man that the Great Wall built by Qin Shi Huang was not what it is now. It was just a tall, thick wall. There are several lookout towers above for sentries to keep watch. There is no beacon tower at all. So where did the beacon tower come from?

It is said that after the Great Wall was repaired, it looked like a big dragon lying across the land of China. Those barbarians who often invaded the Central Plains were blocked outside the city walls and never dared to invade again. In this way, the border was peaceful for several years. In fact, the enemy has not stopped plotting to invade the Central Plains. One dark night this year, the sky was as cloudy as a big black pot, and I couldn't see my fingers. After a while, there was lightning and thunder, and it started raining heavily. Tens of thousands of Xiongnu elite soldiers, led by general Shan Wu, reached the edge of the Great Wall. They set up ladders and quietly climbed up to the city. The people on guard in the city heard no movement because of the heavy rain. Later, a bolt of lightning illuminated the ground, and the sentry discovered that there was a sneak attack. The sentry quickly banged his clapper to call the police. When the sentry at the next station heard the news, he banged his clapper again to spread the news. But that night it was raining heavily, and there was thunder and lightning. You couldn't hear the sound of banging clappers! Later, the sentry on guard was killed by the Huns. The Huns crossed the Great Wall, opened the city gates, and let in tens of thousands of elite soldiers. Suddenly, the northern border was in a hurry.

When the news reached the palace, Qin Shihuang quickly sent troops to resist when he saw the urgent news. The person leading the army was General Yuan Mu. Yuan Mu led his troops on the road day and night. In the Shandong area, they encountered the Huns soldiers who invaded the Central Plains. After the war, the two sides were at a stalemate. When Yuan Mu saw that this was not going to work, he used a strategy. He first asked some people to dig some big holes on the road, and then disguised them. He also prepared a lot of dry firewood and set them up in a steep area. A few days later, the two armies faced each other. Yuan Mu pretended to be defeated, turned around and ran away with his troops. Shan Wu thought that the Han people could not resist, so he chased after him and rushed into the capital at once. The Huns' soldiers and horses were running very fast, and they were about to catch up with Yuan Mu's team. Suddenly there was a howl, and the hussars in front fell into the trap. All of a sudden, there was chaos. There were those who pulled the horses, and there were those who rescued them. . When Yuan Mu saw it, he immediately shot back. According to the plan, he blasted all Shan Wu's troops into dangerous areas, burning the Huns' soldiers and horses to death and injury. In the end, the defeated Xiongnu soldiers had to raise their hands and surrender.

Later, Yuan Mu summed up the lessons learned from the fall of the Great Wall. He said to Qin Shihuang: "Although the Great Wall is strong, there are sentries every half a mile to knock bangs to call the police. Not to mention the speed is so slow. When it is windy and rainy, the sound of bangs is drowned out, and the Great Wall is useless." After hearing this, Qin Shihuang felt very worried. unhappy. He deliberately said: "Okay, you are right, then, what do you think should be done?" Before Yuan Mu could speak, Qin Shihuang said again: "I think I will leave this matter to you! If something like this happens again in the future Son, let me ask you a question." When Qin Shihuang came, Yuan Mu was stunned. After all, he was a military general and knew nothing about civil engineering. He originally wanted to report this to the emperor and ask him to send someone to solve it, but he didn't expect Qin Shihuang to leave the whole matter to himself. what to do? The emperor speaks with golden words, who dares to disobey. Yuan Mu thought about it and had no idea, so he agreed to it.

After returning home, Yuan Mu began to think hard about how to quickly transmit the alarm to the commander-in-chief, but after much deliberation, he could not come up with a good solution. One day, it was raining lightly, and Yuan Mu walked up and down the Great Wall distractedly, unaware that the whole day was almost over. He leaned on the battlements and looked into the distance. Suddenly, his eyes lit up and he saw that a village in the distance was lighting up a fire to cook dinner, and wisps of smoke went straight up into the blue clouds. The rain is falling and the smoke is rising. He had an idea and thought: "This village is dozens of miles away from here, and every wisp of smoke can be seen so clearly. Is it okay to use smoke to call the police?"

So, Yuan Mu called the police. A beacon tower was built on the Great Wall, and dry firewood was provided in the beacon tower. After the beacon tower was repaired, Yuan Mu tried it and it worked really well. If there is a situation somewhere, it won't take a while for the commander-in-chief to see the signal and immediately send troops. The Great Wall has become even more majestic since the beacon towers were built. How dare those barbarians act rashly again? So from then on, the border