In the past few days, most of the mountain paths traveled by the field camp were in the dense forests on the ridges and halfway up the mountainside. To ambush the hidden ravine of the Mongol cavalry, you only need to go two miles to the lower left from the hill where you are resting. However, before leaving, Cao Ergou first sent the elite to find out the way, and then killed the sentries of the Mongolian army. The Mongol sentries standing guard, like their horses, were unaccustomed to the hot and humid climate of the south, and were drowsy to the sound of cicadas and the sound of rushing mountain streams, and in the dim darkness they were silently cut by the scouts of the field battalion. In the ravine below, most of the Mongol soldiers sat on the edge of the mountain stream to cool off, and only a few Mongol soldiers and colonels of the newly annexed army swam in the stream - very few Mongols could swim, and the middle and junior officers and soldiers of the newly annexed army were not qualified to swim with the Mongols at all. In this ravine, the Mongol cavalry and the new generals were in the upper reaches of the mountain stream, where the coolest and clearest water seemed to them to be the safest; The horses were tended by a few Mongols in the middle of the creek – either drinking water or being tethered to rest in the forest by the stream; The junior and middle-ranking officers and soldiers of the new annexed army, the fourth class in the eyes of the Mongols, were sent to guard the lower reaches of the creek, where there was the only exit from the ravine, and they were not even allowed to go near the upper reaches of the stream, but only to take the water that the horses had drunk.

The field battalion lurked quietly on the mountainside above the Mongols, waiting for the signal for the attack - artillery fire. Each company of the field battalion carried 12 light tiger squat guns, and five companies were 60. This light tiger squat gun weighs less than 40 catties, and its trajectory is similar to the curve of a mortar, which is especially suitable for mountain combat. Although it is much less powerful than the field artillery, it is not too easy to deal with the Mongols who only wear leather armor. According to Cao Ergou's estimates, there were about 300 Mongols by the mountain stream and stream, 200 at the mouth of the ditch, and about 500 horses. Cao Ergou has a very high talent in fighting, and he judged the situation of the Mongolian army in the ditch to be eight or nine, which is also the fundamental reason why he became the No. 1 general of the Perak Army. In fact, there were 450 Mongol troops in the ditch, including 250 Mongol cavalry, 200 new annexes, and 600 horses. According to Cao Ergou's thinking of one person and one horse, the Mongolian army has 500 people, and the horses should also be 500. But in fact, these 600 horses did not have the mounts of the new annex army guarding the mountain pass, and the extra horses were used to replace the Mongolian army when they charged.

The cries of cicadas and the sound of running water reduced the loud sound of the tiger cannon fired, and the Mongolian cavalry who were lying or lying down heard a dull thud, and they all looked halfway up the mountainside, only to see that the forest on the mountainside had been shrouded in white mist, and when they were puzzled, then dense small iron balls fell from the top of their heads with a sharp whistling sound. In an instant, the crowd in the ravine was shrouded in smoke and dust, and screams and howls rang out one after another. At first, there were wisps of red, then more and more red, and finally the whole stream was dyed crimson. In fact, these Mongols did not lack vigilance, and with the super mobility of their cavalry, they not only had the right to choose and take the initiative on the battlefield, but also had an unparalleled information advantage in reconnaissance and intelligence. Take this Mongolian cavalry as an example, they have three teams of scout cavalry on the official road between Baizhang City and Mingshan City. Once the Thunderbolt army appears, information such as numbers and weapons will be quickly transmitted to the rear, and the hidden Mongolian army will have plenty of time to respond. It's just that what they didn't expect was that Ouyang Xuan didn't take the usual path at all, and would rather spend several times more time and huge physical exertion to take the mountain wilderness path, and coincidentally, their hiding place was discovered by the Thunderbolt Army again.

The light tiger squat cannon is only an itch for targets such as city walls, but it is definitely like cutting tofu for a human body wearing only leather armor. Sixty guns were fired together, and the dispersion of their shotguns covered most of the cavalry, and after the first round of shelling, a third of the two hundred and fifty cavalrymen were killed or wounded. Some of the Mongols who came to their senses grabbed their weapons and rushed up the hillside, while others ran to the tethered horses downstream of the stream. Those who rushed up the mountain were unexpectedly stabbed to death by the spears that stabbed from a high position, and the Mongol cavalry who stepped on the war horses rushed to the mountain pass, but the road in the ravine was rugged and narrow, and the horses could not rush up at all, and for a time it was blocked by water. On the mountain pass, due to the short range of the muskets, the Thunderbolts had to dive closer to the foot of the mountain. It's just that the woods at the mountain pass are sparse and there are few cicadas, and the water is slow and the sound of the water is small, so the new army is more vigilant when it undertakes the task of vigilance, so it was discovered before it reached the range of the musket. These new annexed troops are also the elite of the new attached army in Qiongzhou, and they did not panic when they saw someone attacking, but met them. However, the Thunderbolts who came to attack the pass had three companies, and in addition to the 200 musketeers, there were 100 people who were specialized in throwing grenades. Under the three-stage fire of grenade bombardment and musket fire, the two hundred new annexes collapsed in an instant, turned around and fled out of the mountain. The fastest of them picked up a life, and the slower one was unlucky—trampled to the ground by the horses that rushed behind. The Mongolian cavalry fled for their lives, and even the cavalry of their own tribe who stood in the way were beaten with whips and slashed indiscriminately, who would care about the life or death of these cannon fodder soldiers.

After the initial panic, the Mongols also tried to counterattack but were scattered by the reloaded artillery, so they had to ride their horses and rush down the stream to the mountain pass. There were also a few Mongols who refused to give up their horses, and they thought that the reins were too slow to untie the reins, so they directly cut the rope with their knives. These horses were well-trained horses, and no one rode them, and they followed the Mongols to the whistle and ran out of the mountains. This made Cao Ergou, who was commanding halfway up the mountain, anxious, and asked the soldiers protecting the artillery to rush down and kill the Mongols who cut the ropes of their horses. In his eyes, horses are a very good thing, of course it is better to live, and it is also extremely precious meat when they die. However, by the time the Thunderbolt soldiers rushed to the tethered horses to deal with the Mongols, the horses had already run away, and more than half of the horses had rushed out of the mountain with the Mongol cavalry.

The Mongol cavalry fired arrows as they fled. These Mongols were even very good at riding and archery, and a rain of arrows knocked down a thunderbolt soldier who threw grenades at the mountain pass. Even if it is thrown condescendingly on the mountain, the Thunderbolt grenade can only throw forty or fifty meters, while the effective range of the Mongolian composite bow is about 100 meters. This elite Mongolian army had excellent archery skills, and for a time it suppressed the Thunderbolt army at the mountain pass. The muskets of this era were far inferior to bows and arrows in terms of rate of fire, so Cao Ergou ordered the musketeers to fire from a distance of 200 meters to avoid losses under the bows and arrows of the Mongolian army. Even if the bow and arrow are shot at such a long distance, they are not lethal, but the hit rate of the musket is really not high. Although the Mongolian soldiers and horses were dense and would hit many people and horses in each round of shooting, these Mongolian troops were very fierce in danger, relying on the speed of their horses and not afraid of casualties to break through to the mountain pass, and even let them rush out more than 100 cavalry and more than 100 empty horses.

In this battle, the Thunderbolt army killed more than 50 Mongolian cavalry and more than 50 new annexes, while their own side lost 8 people and 25 were wounded, all of them with bows and arrows. The number of wounded soldiers of the Mongolian army was more than 150, of which 90 were wounded by the Mongolian cavalry and more than 60 were wounded by the newly annexed army. Most of the injuries of the Mongol cavalry were caused by artillery shelling, while the injuries of the new annexes were mostly grenades, but some were also wounded by gunshot wounds and horse trampling. Because they hated the burning and looting of these Mongolian troops at Baizhang Pass, the officers among the wounded were killed on the spot, and the wounded soldiers were driven back to Mingshan City. When carrying out the order to release the wounded soldiers, Cao Ergou ordered the thumb, index finger, and ring finger of the captured Mongol cavalry to be cut off, so that they could neither draw the bow nor hold the knife after they were wounded.