With the passage of time, the French army sappers began to gradually become familiar with the characteristics of the Chinese mines, and they used their bloody experience to figure out that the pressure required for the triggering of Chinese mines is 8 to 10 kilograms, and this weight design is very ingenious, even if some cats, dogs, foxes, rabbits run on the minefield, they will not detonate the mines.

But if you drive a war horse to clear mines, the weight is enough, but the significance is not great, because the pace of the horse is too large, and only a few points are stepped on in a large area, and a minefield can be detonated, which is considered good.

In general, it is still a reliable mine detector. Although the speed is slow, the equipment is simple and has no jishu content, and the working method is more primitive, because of the most reliable effect, until the future 21st century, the mine detector rod is still used in the troops of various countries.

After the sappers adapted to this trigger pressure, on the 26th, the effect of mine detection was greatly improved, and dozens of white circles were drawn in a row, which is the weakness of the standard weapon. On the 27th, this was still the case, and Nigri was in the telescope, watching all this, with a slight smile on the corner of his mouth.

But before the smile expanded, only the familiar "boom" sound, a sapper was blown up again, and then a sapper parallel to him also triggered a mine, this sapper reacted quickly, fell backwards, with a "boom", although his body was blown up flesh and blood, but his life was saved.

Then the soldier who narrowly escaped the disaster reported that he had encountered a trip mine.

The so-called tripping thunder, also known as tripping thunder, does not rely on the pedal to start the ignition device, but ties a tripwire in the grass or on a small wooden stake, about 10mm from the ground. As soon as the tripwire is pulled, the fuse firing pin is unfastened, detonating the mine. Mines are made of a single piece of cast iron with many grooves in it, so that when it explodes, a large number of debris will fly.

Just now, it was the soil detector rod of the French sappers that hooked the tripwire, but now that the French knew about the existence of the tripping mine, they suddenly raised their vigilance and quickly improved their detection measures. The first is to cut down a tree branch about ten meters long, two people hold it together, sweep the ground, and then slap violently, and then Zuihou carefully measures it with a lightning rod.

In this way, after paying the price of more than a dozen sappers killed and wounded, the French army finally gradually approached Daqing Mountain on the 28th, and at the same time, the hot air balloon was constantly observing the defensive arrangement on the top of the mountain, and the artillery unit also continued to shell the target on the top of the mountain according to the instructions of the hot air balloon.

At this time, the Chinese defenders on the hill really felt the pressure, and the French army was effectively clearing the minefield, and it was estimated that a ground offensive would be launched soon.

Commander Su Yuanchun, who had fought fiercely with the French army in Bac Ninh, knew the strength of the French artillery, because the opponent had the cooperation of the hot air balloon in the sky, and could adjust the attack coordinates at any time, and its accuracy was far stronger than that of the Chinese army. How can you deal with the other party's hot air balloon? Since there is no way to shoot down the hot air balloon, it can only be suspicious and interfere with the other party's intelligence.

In order to confuse the other party, Su Yuanchun once suggested to the command headquarters that a large number of fake troops and facilities be deployed. The idea quickly spread in large numbers.

As a result, on the positions of the Chinese army, including the top of this Daqing Mountain, there were a large number of fake soldiers, as well as fake barracks, fake warehouses, fake fortresses, and especially a large number of fake artillery, that is, the trunks of trees with the same length and thickness as the cannons were painted in a similar color and placed as artillery positions, which were staggered with the real positions. As Su Yuanchun expected, these camouflages achieved a very haode effect, greatly dispersing the firepower of the French army and preserving the living liliang.

At this time, he had five infantry battalions and two artillery batteries, totaling about 2,500 men, and 1,500 troops from the Vietnamese Phan Dinh Phong Division. Among them, two battalions with more than 1,000 men were placed on the front of the first line, two artillery companies were placed on the west side of the position, Pan Tingfeng's department was stationed on the east side, and the remaining three battalions were first ambushed in the tunnels in the rear.

By this time the French had advanced down the hill, entered the firing corner of the hilltop battery, and carved out several safe passages in the minefield, and with the order of the commander Laguer, the French began to climb the hill.

Su Yuanchun knew that there was also a layer of mine belt buried halfway up the mountain, and the location was within 300 to 700 meters from the top of the mountain, which was within the range of the mountaintop rifle, which could effectively interfere with the enemy's mine detection. He ordered that as soon as the enemy was within range, all officers and men would obey the order and open fire on the French sappers with sticks.

The French army below climbed faster and faster, and soon approached halfway up the mountain, Su Yuanchun was condescending, through the gun hole of the annular concrete fortification, he did not need a telescope, he could see the enemy's figure clearly, and the one who walked in the forefront was a row of sappers, holding a stick, like a blind man walking on the road, poking and poking everywhere, and more than 20 meters behind, a large number of infantry followed.

Seeing that he was already very close to the minefield, Su Yuanchun shouted, "Fight!" Almost at the same time, a thousand rifles let out a cough. The French troops immediately fell, especially the sappers, who received "special attention", and everyone was shot from several directions, screaming and screaming, either dead or wounded, almost all of them were spared.

Laguer ordered a return fire, and immediately from the French camp, the machine guns spewed out countless tongues of fire, and swept towards the top of the hill, causing the ring of fortifications to fly with rubble and sparks to splash everywhere, and at the same time the French army stepped over the dead and wounded soldiers in front of them and launched an assault on the top of the mountain.

Along the way, no mines were found, which also paralyzed the French army, thinking that there would be no more mines on the hillside, and whether there were sappers or not, they rushed straight to the top of the mountain with a brave spirit.

But soon, they were disappointed, not long after they rushed, a series of explosions sounded, more than ten tripping thunders were pulled and detonated, and a large area of gunpowder smoke and dust, mixed with the flesh and blood of the hands and feet that were blown away, was like a burst of black rain, spilling towards the hillside to split the head and cover the face.

This burst of thunder immediately shattered the illusions of the French army, and Laguer immediately led the team to retreat, and the speed was more than ten times faster than when they came!

Nigri was both angry and helpless, these mines on the hillside were no better than the minefields in front of the mountain, they were all under the cover of fire on the top of the mountain, how could the sappers slowly detect little by little?

After some heated discussions, the French army decided that it was necessary to change to a more rapid method of demining, that is, to use explosives to detonate, but now there was no professional detonator at hand, so it could only be the same as a mine detector.

The specific method is: taking advantage of the dense bamboo forests in the mountains of Vietnam, cutting down a large number of adult bamboos more than ten meters long, because the bamboo is hollow, after opening it, it can be filled with explosives one by one, and the fuse can be connected to become a simple blasting canister. Seven or eight long bamboos are lined up, separated by a few meters from each other, and when they are detonated together, a large open space can be cleared. If you advance in several directions at the same time, you can quickly clear several safe passages.

In this way, demining can be said to be simple and fast, and there is no need for sappers to brave the enemy's fire to detect slowly. But the disadvantages are also obvious, detonating all the way up from the mountainside requires a huge amount of explosives, but Nigri has no more choice.

In the next few days, the battlefield was quiet, and the French army kept cutting down the bamboo, and at the same time opened the joints of the cut bamboo, and filled it with explosives according to the calculated amount.

By July 2, Nigri was roughly ready, making nearly 1,000 bamboo blasters, originally according to his jihua, he was going to build about 2,000, but under Frey's repeated urging, Nigri had to attack in advance.

Late at night on July 2, Su Yuanchun was in his headquarters and boasted to the Vietnamese general Phan Dinh Feng: "The defense of this place is impregnable, and the French will not be able to attack it no matter what." ＂

Pan Tingfeng was born in a family of eunuchs, and became the imperial history of the Ruan Dynasty by virtue of his status as the champion of the imperial examination. Although he did not have much military talent, he was extremely resolute in resisting France, brave and resolute, and honest and honest, and these advantages can be said to be rare among Vietnamese officials, so he was also deeply respected by the Chinese military.

At this time, he believed in Su Yuanchun's cowhide a little: "It's better to be cautious, the responsibility for the defense of this place is heavy, and the general can't be careless." ＂

Su Yuanchun smiled and waved his hand: "Pan Yushi, you are too worried." The French army has always disliked night battles, if we attack us during the day, we will defend our positions with mines, and guard the mines with positional firepower, so that they complement each other, and the French army cannot have wings and fly over in the air, and the imperial history can be relieved."

Before Su Yuanchun could finish speaking, he only heard a loud noise outside, "Boom!" Earth-shattering and deafening. The two faced each other, and before they could react, a soldier rushed in outside and reported: "Report!" The French are attacking me! ＂

Su Yuanchun immediately asked: "Is the enemy army exploring my minefield?" ＂

"The report, there is no mine detection, it seems that strange equipment was used, and the explosion of mines layer by layer has almost no effect. The French army is advancing so fast that it has broken through the mountainside! ＂

Su Yuanchun was shocked!