When the combat sappers retreated, they were left with a lot of mess. For example, they planted all kinds of mines in the trenches dug by the Qing army. More than 100 coats and more than 20 bannermen were killed.

Overnight, nearly a thousand coats and hundreds of bannermen were lost, compared to such a big battle, this loss did not make Huangtai Jiduo sad, such a loss was originally expected. However, the advantages shown by Zheng Jiajun in the night battle made Huang Taiji very worried. Obviously, if heavy troops were not deployed in the area of the trench, the construction could not be continued at night, otherwise, as long as the enemy counterattacked, the coats arranged in front would be equivalent to giving them to others. Although this is also an opportunity for spies or something to sneak into Niuzhuang Castle. However, considering the combat effectiveness shown by the model army and the tightness of the defense of the fortress in front of him, it would be a dream to rely on a dozen or dozens of spies and take out a few swords, so as to grab a key position and open the opponent's defense in one fell swoop.

However, if heavy troops are deployed in the area of the trench, these soldiers must also be deployed in the trench, otherwise, the artillery on the opposite side is not the level of the ordinary Ming army. In addition, if the heavy troops are to be deployed in the trenches, it is necessary to dig out a large area for hiding troops in the trenches, which will greatly delay the progress. Although it is only a day's distance from the enemy's first trench, even after the first trench, there are still several trenches behind it, and the subsequent advance still needs to rely on such means as excavation. Winter has arrived, and when you wake up one night, the temperature outside has dropped to the point of dripping ice. Then, in a short time, the ground will freeze and become as hard as stone, at which point the excavation will become completely impossible.

Huang Taiji asked the generals below to discuss this issue, but there was no result for the time being. But there was no waiting on the battlefield, the weather was getting colder, and with each passing day, the tunneling became more difficult than the day before.

However, the daytime excavation also ran into trouble. Because of the closer, some of the Model Army's other weapons can also come in handy. For example, the Manchu army had already seen the shrapnel of this kind of artillery shell, which had a curved trajectory, and as long as the landing point was accurate, it could be quite effective against targets in the trenches. The artillery of the Model Army conscientiously hit the grid and conducted test firing at various targets outside Niuzhuang Fort. Therefore, the accuracy of the attack on the target is not a problem at all, and often after one or two rounds of test firing, the model army can quite accurately hit the shrapnel over the trench. In the beginning, almost every shrapnel that knocked down the target caused a lot of casualties. The Qing army's excavation also slowed down suddenly.

However, shrapnel is not indefensible either. The Manchus immediately responded. They modified the shield cart. The thick planks were changed from blocking the front to being erected on top of them, so that they could effectively resist the blow of shrapnel shells. And those coatings or something, you can hide underneath and continue to dig. The transformation was fairly simple, so after only an hour of shrapnel strikes, the Qing offensive resumed.

However, the Model Army is not completely unprepared for this situation. When the trench of the Qing army continued to approach about seventy or eighty steps from the first trench of Niuzhuang Fort, hundreds of clay pots were suddenly thrown from behind the first earthen wall of the model army.

These pots were ejected with a stone thrower hidden behind an earthen wall. Yes, it's an antique stone-throwing machine. Compared with artillery, the catapult has a limited range, insufficient power, and the accuracy of the strike is also a mess. So when artillery began to appear on the battlefield, the catapult was quickly thrown into the garbage heap of history.

But compared with artillery, in fact, the catapult still has some advantages of its own, for example, when it fires projectiles, it has a long acceleration time and a small overload, so it can be used to project those structurally fragile things. For example, during the Mongol expedition to the west, the Mongols used a catapult to project hornet's nests and the corpses of people who died of plague on the walls of the enemy with a catapult. And these things, apparently, are not capable of being fired by artillery.

At this time, the same is true of the clay pot projected by the model army. These clay pots are filled with light crude oil from Borneo. The quality of crude oil produced in Borneo is quite good. It contains very little bitumen, has very good fluidity, and can even be used directly as fuel for steam engines even without refining. In another time and space, during World War II, Japan, which lacked the ability to refine oil, often let its warships directly use Borneo's crude oil as fuel. Of course, this is not without problems, and Borneo's crude oil has too many light volatile components and is very flammable. Normally fine, but once a warship is hit and damaged, these light crude oils can easily ignite and lead to a devastating fire. The fire damage management has always been the weakness of the Japanese army, so in the war, the loss of many warships of the Japanese army was related to the fire caused by this crude oil.

Here, however, this property of this crude oil is ideal for arson. The clay pots were thrown by the stone thrower at the target a hundred paces away, and they crackled and smashed near the trenches that the Qing army was digging, and some of them smashed directly on the modified shield carts in the trenches, and then the raging fire burst into flames. These fires are different from ordinary flames, if they are ordinary flames, they may be able to burn the shield cart, but the people under the shield cart still have a chance to escape. But this flame is different. They are burned on crude oil that can flow. The crude oil flowed downward, and the flames flowed downward, and in an instant, the entire shield car was completely engulfed by the fire, and the people under the shield car naturally had no survivors. The blazing flames also made any rescue impossible.

This blow brought the Qing army's excavation to a complete halt that day. Even after the flames were completely extinguished, the Qing army did not resume the excavation, and until the evening, the observation posts on the tower showed no sign of the enemy resuming the excavation. But at dawn, the dogs deployed at the front of the Model Army barked wildly. Immediately after that, the soldiers heard the sound of the alarm bell, and as soon as the troops on duty were ready for battle, a large number of Qing troops emerged from the trenches dozens of paces away.

At the same time, the artillery of the Qing army also began to fire fiercely at the earthen walls and artillery bases of the model army. In the second half of yesterday night, the Qing army quietly pushed more than 20 imitation Hongyi cannons to a place only a few hundred steps away from the earthen wall. In addition to these imitation Hongyi cannons, the Qing army also invested more than 40 small cannons, and for a time the earthen walls were full of dust stirred up by cannonballs.

Taking advantage of this round of artillery fire, the Qing army quickly rushed to the front of the first trench. They quickly set up the long ladder on the trench, and the soldiers behind rushed straight over the ladder. Ahead of me was the first barbed wire fence and earthen wall.