The Silk Road was once an important source of economy for the Persian Empire in western Asia. The huge profits gained from the Silk Road trade were one of the important reasons for the prosperity of the Persian Empire in the central area of the Eurasian continent for a thousand years.
On a plateau west of Turpan in Xinjiang, China, stands the magnificent ruins of Jiaohe Ancient City. The buildings inside the city are divided into functional areas, which is consistent with the cities in the Central Plains at the same time. In 640 AD, the Tang Dynasty established the Anxi Protectorate here to manage military and political affairs in the Western Regions. After the Tang Dynasty unified the Western Regions, the trade between China and the West became increasingly close. At this time, the Silk Road opened by the Han Dynasty reached its peak in trade, forming three main lines of north, central, and south, as well as multiple branch lines north and south of the Tianshan Mountains. In order to protect the Silk Road, the Tang Dynasty established a sound military and political system in the Western Regions. In 685 AD, the Tang Dynasty moved the Anxi Protectorate from Xizhou to Kucha, a military and political management institution located north of the Tianshan Mountains and south of the desert, becoming the protector of the Silk Road. The Tang Dynasty radiated its defense along the Silk Road with the Anxi Protectorate as a center, and set up garrisons in the important passes of the Silk Road, such as the Luntai City more than 100 kilometers to the east, the Tangwang City 80 kilometers to the southeast, the Tonggusibash City 40 kilometers to the southwest, and the Kumutula City 30 kilometers to the northwest. There were guard posts between the towns, and beacon towers were set up 10 kilometers in front of the towns and guard posts, guarding the traffic of the Silk Road.
Rulers of Tang Dynasty reformed heavy cavalry into light cavalry, which was flexible and agile. Therefore, no matter which direction the enemy invaded Kucha or the Silk Road from, the Anxi Protectorate could rely on the garrisons and beacon towers to launch long-range raids.
In 661 AD, the Tang Dynasty set up the Persian Governorate under the jurisdiction of the Anxi Protectorate and appointed Beilusi as the governor. The Persian prince who fled finally received the protection of the Tang Empire. However, the Arab cavalry did not give up hunting the Persian prince. He fled all the way to the end of the Silk Road: the Tang Dynasty's capital, Chang'an. Chang'an was the largest city in the world at that time, with a population of about one million in an area of 84 square kilometers. Among these people were many merchants from India, Iran, Syria, and the Arabian Peninsula, as well as a large number of students from Korea and Japan. The emperor even set up exclusive blocks for princes from the Western Regions. The taverns opened by the Sogdians could be seen everywhere in the western part of Chang'an. Here, not only were there drinks and fine wines from the Western Regions, but also Hu people songstresses who were good at playing instruments and singing.
About 40 kilometers west of Shanshan County in Xinjiang, there is a square-shaped beacon tower site with a side length of 17.8 meters and a height of 11.1 meters. The entire beacon tower is made of rammed earth and consists of two parts: the outer building and the central building. The central building has four floors for living quarters. This is currently the best-preserved and largest Tang Dynasty beacon tower in China.
On the northern edge of the Taklamakan Desert, there is another Tang Dynasty beacon tower made of rammed earth, with a remaining height of about 14 meters and a base width of about 7 meters. Round wooden stakes are placed in the rammed earth layers to increase tension, allowing the beacon tower to stand for more than 1000 years. The Tang Dynasty set up a large number of beacon towers in the Western Regions. Even today, beacon tower sites left by the Tang Dynasty can still be found in the valleys between the Tianshan Mountains, the Pamir Plateau, and beyond. These beacon towers were either built in precarious locations or on open platforms, with a spacing of about 13.5 kilometers. If there were mountains or complex terrain, there was no limit to the distance between them, but they had to be within sight of each other. Beacon towers near the border would also have fortifications built around them to strengthen defense. The Tang Dynasty was the most prosperous period of the Silk Road. This international trade route connected the capital Chang'an with Central Asia, West Asia, and Eastern Europe, weaving a huge transportation network. Along this trade route, there was extensive and in-depth communication between the East and the West. At the same time, a special way of cultural exchange was quietly taking place.
In March 708 AD, in order to control the northern border, the Tang Dynasty built three castles named "Shouxiang Cities (the city to accept the surrender of the enemy)" on the north bank of the Yellow River in the southern Yin Mountains, together with surrounding towns, to construct a defense system inside and outside the Hetao region, which posed a strong deterrent to the threat of the later Turks and Tibetans. Today, in the north of Tokto County in Inner Mongolia, some mounds can still be seen, which are the remains of the Tang Dynasty's East Shouxiang City. Due to its proximity to the Yellow River and the loose soil, this former northern border has been completely washed away by rain two years ago. The three Shouxiang Cities were more than 200 kilometers apart and relied on each other, with 1800 beacon towers set up to create communication and coordination between the east and west. From then on, the Tang Dynasty expanded northward by more than 150 kilometers, and the later Turks dared not cross the Yellow River to graze, reducing the threat to the Tang Dynasty.
The Shouxiang City is not only a military engineering project, but also a place for trade between the Tang Dynasty and various ethnic groups in the north. It has become a frontier base for national exchange and integration. By the time of the Kaiyuan period, the Tang Dynasty was unprecedentedly strong in national power and military strength. With the enhancement of military strength, the Tang gradually gained the advantage in the war against Tubo. After the Battle of Talas, the Arab Empire gave up its expansion towards East Asia. Among the Tang prisoners of war captured by the Arab Empire, there were many excellent craftsmen. They were brought by the Arab army to the Central Asian world. Shortly after the end of the war, under the guidance of Chinese craftsmen, the first paper mill and porcelain kiln were established in Central Asia. The secret production process of silk also began to be openly taught. These products became the most important commodities for Arab-European trade. Through the seemingly ruthless way of war, human beings have gained extensive and in-depth communication.
The warning system of the Tang Dynasty was very complete. From the capital Chang'an to the northern border, there was a beacon tower every 15 kilometers. These beacons could transmit signals for 1000 kilometers in one day and night. Since the rebels in the northeast border approached the northern defense line of Chang'an, the beacon towers have been lit every night to report safety.
In the Chinese Great Wall resource survey that began in 2006, these beacon towers on the land of Xinjiang were included in the scope of the Great Wall, thus refreshing the concept of the Great Wall. The survey results showed that there were more than 300 beacon towers left over from only the Han and Tang dynasties on the land of Xinjiang. These beacon towers, standing in the heavy wind and sand of the Western Regions, are landmarks of the Silk Road. They are not only military facilities, but also safe havens for protecting merchant caravans and replenishing supplies. During the Tang Dynasty, the beacon towers were more adapted to China's need for opening up foreign exchanges, changing from "defensive" to "welcoming" and from closed to open. This was an important measure for the central dynasty to rule the Western Regions, playing a dual role in protecting the border and keeping the ancient Silk Road unobstructed. Today, these ancient beacon towers, which have witnessed the smoke of war and listened to the bells of merchant caravans, are like a unique historical record of the changes of the Silk Road and the political and economic situation of the Western Regions. The Tang Dynasty was the golden age of commerce in ancient Chinese history. At that time, more than half of the world's famous commercial cities were concentrated in China. The capital Chang'an and the accompanying capital Luoyang became world metropolises. Under the protection of the beacon towers belonging to the Great Wall defense system, the trade of the Silk Road reached its historical peak, becoming a place where Chinese civilization, Persian civilization, and European civilization intersected. In the vast area connected by the beacon tower system, the Tang Dynasty gave a new meaning to the concept of "China", forming a new and large multi-ethnic country in this unique era. "China" no longer represents a race defined by bloodline, but rather identifies with a common cultural tradition, presenting a diverse population.
