In ancient wars, if you want to control Liaodong area, you must pass through here.

Open the topographic map of China, and the towering Yanshan Mountains separate the Central Plains from the Northeast. This vast mountainous area has always been an obstacle between nomadic people and agricultural people, and it also has a very important position in the military. In ancient and modern wars, this place is often a battleground for military strategists. From ancient times to Ming and Qing dynasties, whether the northern regime wanted to go south or the central plains regime wanted to control Liaodong, it had to pass through three hubs in Yanshan area.

These three hubs correspond to Tangshan, Beijing and Qinhuangdao respectively.

Before the Tang Dynasty, the main hub of the Central Plains leading to Liaodong was in Tangshan. Until today, we can still see the original northward route in xifengkou, which was called Lulong Road by the ancients.

This ancient route has always been linked with the fate of Luanhe River. It can be said that this road is just for people to walk out along the river bank at the south foot of the journey, turn east after passing Yanshan, and then enter the northeast with the river. Because, this northward route promoted the long-term prosperity of Ji Cheng, and finally, it made the city last for nearly a thousand years, and once became the core city of Yanyun.

With the gradual rise of the Qidan nationality in the northern region, in order to get rid of the control of Lulong Road, they re-opened their own new route-Gubei Road.

It is because of this road that the Khitans can invade sixteen states from the south. In order to completely control the traffic arteries in Yanshan area, the Khitan rulers began to rearrange the Gubei Road connecting themselves with the rear area.

The starting point of this traffic trunk line is in Beijing today. It passes through Gubeikou from Shunyi County, travels south in Miyun County, bypasses the Luanhe River, and directly turns to Heping Spring County in the east, connecting them together. At this place, it meets the original Lulong Road and reaches today's Chifeng area northward.

Moreover, the Laohahe River can provide them with the next way forward, directly to their base camp Zhongjing.

Every traffic change will lead to the rise and decline of a large number of cities along the way, and those hub cities that originally occupied geographical advantages are likely to decline because of the deviation of traffic trunk lines. Liucheng is the best proof of this statement.

It was once the central hub of the Tang Dynasty to control the northeast region, and it was located at the throat of Lulong Road, which was of great strategic significance. However, with the large-scale development of Gubei Road in Liao Dynasty, its position became insignificant. Until today, this area still belongs to a place with relatively weak development level in Liaoning Province, which was influenced by the change of traffic trunk lines in that year.

During the Ming and Qing Dynasties, the imperial court gradually discovered the important strategic position of Shanhaiguan, so it reopened the coastal highway, the third traffic trunk line connecting Northeast China.

As can be seen from the name of this route, it starts from Beijing and goes east along Shanhaiguan until it enters the northeast. It can be said that until today, this route is still an important traffic trunk line connecting the Northeast and the Central Plains. In modern history, people generally refer to Northeast China as "kanto region", which shows that Shanhaiguan is actually the throat of Northeast China.

It was precisely because of the loss of Shanhaiguan in the Ming Dynasty that the North China Plain was completely exposed to the Qing army, which enabled them to March in.

After the establishment of the Qing dynasty, the northeast was banned. Until the late19th century, a large number of talents from the Central Plains were allowed to enter the vast area of Baishan Blackwater due to Russia's eyeing. This large-scale immigration movement is called "crossing the Kanto" in history.

The biggest feature of farming people is that they like to stick to one acre and three points, and are willing to live a quiet life of "wife and children fever". It really takes a lot of courage to be a wanderer far away from home, work hard and explore the new world, and it is widely accepted as a social custom.

The East Gate of Shanhaiguan City defines the land outside Shanhaiguan and the Central Plains. During the hundreds of years from the Qing Dynasty to the Republic of China, people who left their homes in Shanhaiguan, Shandong and other areas began to venture eastward. Of course, it is precisely because of this large-scale migration that the proportion of ethnic groups in Northeast China has changed greatly, and the proportion of Han nationality in this ethnic minority gathering place has soared.

The transportation trunk line on which this kind of population migration depends is the "coastal highway", and the highway and railway networks in Northeast China are also developing rapidly. It can be said that this still has a great influence on the traffic and urban layout in Northeast China today.

The Millennium development and changes in Yanyun are closely linked with these traffic lines, which are also the witness of the exchange and integration between Northeast China and Central Plains. They promoted the economic ties between the two places, transported salt, cattle, sheep and livestock to the Central Plains and even the southern region, and brought a large number of Han people from the Central Plains to the northeast region, forming a new situation of multi-ethnic prosperity.

It can be said that whether the city's traffic is developed or not can be used as a standard to judge the level of urban development, and there is a strong correlation between them. The rise and fall of traffic trunk lines affect many surrounding cities, and this correlation is stronger in the case of extremely inconvenient traffic in ancient times.