Just as Zhou Lin was sitting in a carriage and going to school to sing northern Shaanxi folk songs, the Japanese prison guards in Yan'an received an order from Yamada to attack the protest rally venue of the 'Southern Anhui Incident' in Yan'an on the 20th.

TNT explosives had been transported into Yan'an in batches, but Mr. Fang had deliberately let them in.

The prison guards and Lao Wang of Rite have been monitored, and the people at the contact point in the town have also been monitored, and their every move is under the supervision of the soldiers of the Eighth Route Army.

Even the explosives they transported in several batches, Mr. Fang was clear.

"I checked, and there was no way to get in, let alone install explosives." Lao Wang took a sip of water and said.

"Yes! This task is particularly difficult, since the failure of poisoning, Yan'an has been much more vigilant, just to guard against us people. The prison guard said.

"We'll report this to the generals and see what they can come up with." Lao Wang proposed.

"That's the only way to do it, and we can't think of a good way."

As soon as their request reached Yamada's hand, Yamada immediately called a meeting of the think tank to explore how to send explosives into the Yan'an venue under tight defense.

"General, I came up with an idea." A Shao Zuo said.

Yamada motioned for Shaozo to continue, and asked everyone to give advice.

"My method is to set up a gravity stone throwing machine 800 meters away from the venue, turn the stone throwing into explosive bags, and throw the ignited explosive bags into the venue one by one." Shao Zuo said.

Gravity trebuchet, return cannon, counterweight trebuchet, counterweight trebuchet (name Countereight Trebuchet, Trabutium), developed from the Chinese human trebuchet, first appeared in Europe in the late 12th century in the Middle Ages a trebuchet, a kind of largest trebuchet, the Southern Song Dynasty with Mongolia introduced to China.

Using the principle of lever, one end is equipped with a heavy object, and the other end is equipped with a stone projectile to be launched, before launching, one end of the ammunition must be placed with a winch, a pulley or directly pulled down by manpower, and the other end with a heavy object is also rising at this time, after putting the stone bullet let go or cut the rope, let one end of the heavy object fall, and the stone bullet is also thrown out of the situation, this kind of stone throwing machine is introduced to China through the *** area and is called "return cannon".

By the mid-14th century, some stone throwers were capable of throwing projectiles weighing nearly 1,000 pounds (about 454 kilograms), which was extremely powerful.

Tests have shown that the boom is 50 feet (about 15.2 meters) long, and the 10-ton counterweight can eject 200 to 300 pounds (about 90-136 kilograms) of stone projectiles about 300 yards (about 474 meters).

One or more objects can be thrown, and the objects can be boulders or gunpowder weapons, or even poison or filth.

"Great idea! Only 10 kilograms of explosives are installed at a time, and the angle is tilted, and it is estimated that it should be able to throw about a thousand meters. A Japanese soldier Nakasa said.

"Even if it's not a thousand meters, it's eight hundred meters. At a distance of 800 meters, by the time the Communists found out, our warriors had already completed their mission and retreated. A big Zuo said.

Yamada was also relieved from a few days of depression, and he immediately ordered: "Let's make a simple gravity stone thrower in Mingzhu first, and all the materials will refer to the existing materials in Yan'an, and after the test is successful, tell the latent warriors in Yan'an all the production methods, materials, and precautions, and let them make a gravity stone thrower." ”

Yamada asked a big Zuo to take charge of the matter, and after completing the test in one day, he sent the data to Yan'an.

A day later, the prison guards who received Yamada's telegram excitedly came to report the good news to Wang.

"Gravity stone thrower, this thing is good! Without us getting closer, we can complete the task of delivering explosives packs at a long distance. Lao Wang praised.

"The point is that we can evacuate as soon as we finish projecting. When the Eighth Route Army came to the door, all that was waiting for them was the launch frame. The prison guard laughed.

So, according to the prompts of the message, the two men drew a sketch of the gravity stone thrower.

"Where should I put this launch site?" The prison guard asked.

"That guy who often comes to me to cheat on food and drink has recently been to Yanchuan and will not come back until ten days later. We can take advantage of his dwelling. Lao Wang said.

"What kind of residence is he?" The prison guard asked unclearly.

"In front of his cave, he surrounded a courtyard with a high wall, and we set up a gravity stone thrower in the yard so that it would not attract people's attention. What's more, his house is relatively remote, and few people go there. Lao Wang introduced.

"That's good! We went buy some trees and made them on the spot in his yard. ”

"No, you don't! He was very greedy, so he fished a lot of big trees and piled them up by the yard, preparing to build a new house in the future. We can use those trees, just buy some accessories and come back and make them. Lao Wang said proudly.

"That's fine! Tomorrow is the 20th, let's do it tonight, get that launch pad ready, tomorrow they celebrate, and we'll go and have a good time. The prison guard smiled hideously.

The two men immediately left the old king's residence and ran back to the east of the city.

The soldiers of the Eighth Route Army, who were following, followed them until they reached a remote place and saw them climb over the wall and enter a courtyard.

"You continue to monitor, and I'll report to the chief." After one of the cadres finished explaining, he left the monitoring point.

When Mr. Fang heard the cadre's report, he came to the monitoring point with the cadre.

"What's going on now?" Mr. Fang asked as he held the binoculars.

"They did carpentry work in the yard." Another cadre replied.

In the binoculars, Mr. Fang saw the prison guards and the others placing a long tree on a tripod to fix it.

"What are they doing here?" Mr. Fang didn't understand, and neither did the others.

Time passed quickly, and in the blink of an eye, it was January 20, 1941.

Mr. Fang kept watch all night, and when it was dawn, the two of them went out in batches.

When they went out, one of them stayed in the yard, which gave Mr. Fang, who wanted to find an opportunity to enter the yard to investigate the situation, a headache.

The two people who went out came back with large packages, and then hid in the house and never went out again.

It was already seven o'clock, and there was still an hour before the meeting began at eight o'clock.

"They're moving!" One of the fighters shouted.

Mr. Fang and the others immediately walked to the observation position, picked up the telescope and observed.

In the binoculars, the two prison guards pressed down one end of the tree like children, and then let go, and the other end was tied to a bag containing heavy stones and sank downward, and the old Wang, who had no time to let go, took it into the air.

"I remembered what it was!" One of the fighters immediately shouted.

"Say it! What is it? And they all looked at the little warrior.

"The bandits in our mountains have this thing, and they use it to throw stones into the distance, and the stones thrown can kill people." Said the little warrior.

Mr. Fang suddenly patted the little soldier on the shoulder: "You have made meritorious service." ”

Mr. Fang turned back to the unsuspecting cadres and fighters and said, "The Japanese spies are going to use this gravity stone thrower to drop explosives bags on the rostrum of the venue. ”

When everyone heard this, they were anxious: "Chief! Catch them quickly, don't let them wreak havoc. ”

Mr. Fang looked at his watch: "There is still half an hour to leave the meeting, and we will surround it." Surrounded by a single agent. ”