Beimeng is located in the northern part of the Mongolian Plateau, with an average altitude of about 1,600 meters. The western, central and northern parts are the Altai Mountains, the Hangai Mountains, the Tangnuula Mountains, the Eastern Sayan Mountains, the Gobi Altai Mountains, the Kent Mountains and other barriers, and the main peaks of each mountain range are generally above 3,000 meters above sea level.

Between the mountains are inland water systems, lakes and basins formed by grabens. The Selenga River and its tributary, the Orkhon River, are the main rivers. The area near rivers and lakes is full of water and grasses, and is a natural pasture and a major agricultural area.

The southeastern part of North Mongolia is a relatively flat plateau, with low hills and shallow basins, and the surface is mainly coarse sand and gravel "Gobi".

Most of the northern Mongolian region belongs to the temperate grassland climate of the mainland, with obvious seasonal changes, long winters, and often heavy snowstorms; The summer is short, and the temperature difference between day and night is very large; Spring and autumn are extremely short. The frost-free period is between June and September, with only more than 90-110 days.

The capital of Northern Mongolia, but also the largest city in Northern Mongolia, and it can even be said that it is the only place in Northern Mongolia that can become a city at this time - Kulen, located in the upper reaches of the Tula River Valley, with rolling mountains on both sides in the north and south, and the clear Tula River flows slowly from east to west from the foot of the Bogdo Mountain in the south of the city, and the east and west sides are the vast and narrow Krulun River Valley Grassland and the Tula River Steppe.

The main neighborhood of the city of Kulen is located on the north bank of the Tula River. The urban area is laid out along the Tula River in the shape of a long strip. The Selbo River meanders north to south, dividing Kulun into two parts: east and west of the river. The urban area on the north bank of the Tula River is divided into three terraces: the first plateau is 1,880 meters above sea level and 2,700 meters wide; The second platform is 1,290 meters above sea level and 2,300 meters wide; The third plateau is 1,300 meters above sea level, with an average altitude of 1,351 meters, and the width of the urban area is only a few kilometers.

In September 1931, it was a good time for autumn to be crisp in the interior, but in Northern Mongolia, the weather at this time was unpredictable, and the temperature often dropped suddenly and sharply, and even snowed. The temperature difference between day and night is greater, and frost often appears in the morning.

Standing on the Bogda Mountain, the endless green grasslands on the east and west sides of Kulen have all turned golden yellow at this time, especially the half-human height and yellowing pastures in the valley of the Krulun River twenty or thirty kilometers wide in the distance, under the gentle east wind, like golden waves, surging, endless, and very spectacular.

The Mongolian oak, which has lost its leaves, grows in abundance in the mountains, and its gray trunks are about 30 meters high, and they stand like javelins. At the foot of the Bogda mountains, the rivers Tula and Selebo, shining with silver light, flow quietly. The beautiful and cold plateau scenery makes people feel refreshed and happy, and they forget to return.

In the midst of this, the rolling hills on the Bogda Mountains to the south of Kulun and to the north, as well as on the Dugang Mountains around the city of Kulun and in the middle of the Krulun and Tula valleys more than a dozen kilometers east of Kulen, were dusty and full of people digging trenches and building fortifications, numbering more than 100,000 people. This is the officers and men of the engineering corps and the troops of Liang Zhongjia and Wang Bi rushing to build the fortifications of Kulun City and the fortresses and auxiliary fortifications around Kulun.

At this moment, on the platform on the highest peak of Mount Bogda, more than a dozen generals wearing grass-green military uniforms and carrying gold stars on their shoulders, surrounded by a large group of guards and staff officers with drawings in their hands, are carefully observing the terrain around Kulen and the fortifications under construction with high-powered telescopes in their hands.

Among this group of people, there was one person who seemed very special, although he was also wearing the grass-green uniform of the Fourth Route Army, with the rank of lieutenant colonel, but his high nose and deep eyes, blonde hair and blue eyes, he was undoubtedly a foreigner.

This foreigner in his 50s is none other than Ludendorff, a military engineering expert hired by Song Zhewu from Germany, a former lieutenant colonel of the German Wehrmacht, and the current leader of the defense engineering expert group of the Fourth Route Army.

Ludendorff came to report on the progress of the defense project to Li Wentian, commander of the Northern Mongolian front, who was inspecting the defense of Kulun. Around them, there were also Gao Zongbao, the commander of the Kulen defense, Liang Zhongjia, the commander of the 43rd Army, and Wang Bi, the commander of the 49th Army.

According to Ludendorff's introduction, the Kulen defense system designed by him was mainly composed of three fortress groups and ancillary supporting fortifications.

Among the three fortresses, one is located at the foot of this Bogda Mountain, one is located in the middle of the Krulun and Tula valleys more than ten kilometers east of Kulen, and one is located in the 180-degree bend of the Tula River Valley, more than 100 kilometers west of Kulen.

If the Soviets were to attack Kulen from the north of Kulen, they would have to go west from Zonghara, then along the Tula valley through the big bend, and then turn east before going straight to Kulen. That is, the Soviet troops in the center, who crossed the border from directly north of Kulen, launched an attack on Kulen in the direction of the attack on the west of Kulen.

Although the road is long, it is better to march along the river valley. And this fortress group, built at the big turn, just chokes this pathway.

If the Soviet army in the center did not take this road, there was a second way to reach Kulen, which was to go directly south into the mountains at Zonghara. It's just that this road has to be traversed in high mountains, and there are no main roads, only mountain paths, which cannot be passed by vehicles and cannons at all.

Therefore, if the main force of the Soviet army in the center wants to attack Kulen, it can only go through the river valley, and if it cannot take this No. 1 fortress group at the big turn, the main force of the Soviet army in the center will never reach the city of Kulen.

The No. 2 fortress group on Dugang Mountain, in the middle of the Krulun River Valley and the Tula River Valley, more than ten kilometers east of Kulun, can just block the Soviet army on the eastern road that invades Kulen along the Krulun River valley to the west.

The No. 3 fortress group, located on the Bogda mountain south of Kulun, overlooks the whole city of Kulen, not only the Soviet troops attacking under the city of Kulen will face the fire of the fortress group, but the artillery fire of the fortress group can also pass through the Kulen and provide fire support to the defense line in the mountains north of Kulen. Even if the Soviet army from the north of Kulun over the mountains and mountains breaks through the defense line of the Fourth Route Army north of Kulun, it will face the fire of the fortress group of Bogda Mountain, and if it wants to attack the city, the price will be very large.

Although Ludendorff is in his fifties, his body is still very valuable, and his facial expression is always a stereotypical demeanor, and he is completely a typical virtuous person.

"Your Excellency Commander, the terrain of Kulen is too conducive to defense, if these three fortress groups are all completed, they are enough to withstand the attack of hundreds of thousands of Soviet troops, and this place can completely become the Verdun of Asia, and it will be another meat grinder."

From Ludendorff's confident tone, it can be felt that he is extremely satisfied with the Cullen defense project designed by him.

Li Wentian took the telescope away from his eyes, nodded and said: "Yes, the terrain here is very good, especially the fortress group designed by your expert group is better, and our Commander-in-Chief Song said yes after seeing the map." It was very difficult for the Soviets to take Kulen. Now, I'm confident in holding on to Cullen. ”

The corners of Ludendorff's mouth curled slightly, and a rare smile appeared, obviously happy in his heart.

(To be continued)