In the special history under the Nguyen dynasty, the name "Trấn Tây Thành" was used to refer to the land of Nam Vang, which is Phnom Penh today and part of Cambodia's territory. But why was it called that and why did Vietnam name the land of another country? To understand more clearly, let's go back to the 17th and 18th centuries. At that time, Cambodia was not a strong nation like today. They were caught between Đại Việt and Xiêm La, which is Vietnam and Thailand now.
What about the internal situation in Cambodia? The kings, princes, and nobles in Cambodia continuously fought for the throne. Today this king ascends the throne, tomorrow he is overthrown by cousins or other nobles. The country was always in a state of turmoil, with ongoing internal wars. Therefore, Cambodian kings often had to seek help from the two neighboring countries, Vietnam or Siam. And this was the opportunity for Vietnam, especially the Nguyen lords in the South, to step onto the historical stage. By the early 19th century, when the Nguyen dynasty officially came to power, King Gia Long and later King Minh Mang decided to take the relationship with Cambodia in a different direction.
In the early 19th century, the Hue court officially named the land of Nam Vang and some neighboring areas of Cambodia as Trấn Tây Thành. "Trấn" was an administrative unit in ancient Vietnam similar to a large province or an area directly managed by the court. "Tây" means west because Cambodia is located to the west of our country. "Thành" here refers to Nam Vang, the capital of Cambodia, which is considered the political and economic center of the region.
Thus, the name Trấn Tây Thành reflects a great ambition of the Nguyen dynasty, turning Cambodia into a dependent territory, almost like a province of Vietnam under the direct management of the Hue court. This was how the Nguyen dynasty wanted to consolidate its influence in Southeast Asia while preventing Siam, the biggest rival at that time. Another interesting detail is that the name Nam Vang was also given by the Vietnamese. In Khmer, the capital of Cambodia is called Phnom Penh. It originates from a legend about an old woman named Phnom, who found a statue of Buddha in a tree, but the Vietnamese called it Nam Vang.
"Nam" means south, while "vang" means prosperous and brilliant. This name reflects the importance of the region in the eyes of the Vietnamese, a political, economic, and cultural center in the south. In summary, Trấn Tây Thành is not just an administrative name but also a symbol of the Nguyen dynasty's ambition to control Cambodia. Speaking of the Nguyen dynasty's rule over Cambodia, we must mention a dramatic period in history from 1813 to 1847. This was the time when the Hue court truly laid its hands on Cambodian land. Especially under King Minh Mang, who had extremely aggressive policies.
At that time, when King Lan Xang II of Cambodia ascended the throne at the end of the 18th century, with the help of the Nguyen lords in the South, Lan Xang was caught in a very tense dispute over the throne with his relatives. He was not strong enough to resolve it himself, so he had to seek help from our army. The generals led troops to help Lan Xang regain the throne. But helping someone cannot be for free; in return, the King of Cambodia had to accept becoming a vassal king, meaning he could still be king but had to obey and be under the protection of our country.
By the time of King Gia Long, the Nguyen dynasty officially named Trấn Tây Thành and sent officials and soldiers to station in Nam Vang. They built fortifications and organized forces to control the area. But the climax of the story was under King Minh Mang when he not only wanted to protect Cambodia but also wanted to completely assimilate this country. This was when everything became tense. King Minh Mang was famous for his idea of a unified Đại Nam. He wanted all the lands under the control of the Hue court to bear the distinct marks of Vietnam, from culture, customs to social organization. With Cambodia, he applied a series of policies that the Khmers called "Vietnamization."
The Khmers were required to dress like the Vietnamese, meaning abandoning traditional Khmer clothing, wearing the áo dài, and tying their hair in the Vietnamese style. Even Khmer officials had to learn Vietnamese and perform court rituals in the Vietnamese style. The Nguyen dynasty organized Cambodia into provinces and districts similar to the organization in Vietnam. They sent Vietnamese officials to oversee all activities, while Khmer officials were almost sidelined, only doing minor tasks. These policies may seem like modernization or unification, but in reality, they made the Khmers feel oppressed.
Because of these harsh policies, it is not surprising that the Khmers began to rise up. In 1841, a major uprising broke out in Cambodia led by Khmer nobles and monks. At the same time, Siam, our long-standing rival, saw this as a golden opportunity to intervene. They supported the rebels by sending troops to Cambodia with the goal of overthrowing the influence of the Nguyen dynasty and bringing Cambodia under their protection. Until King Minh Mang passed away in 1841, King Thieu Tri ascended the throne and clearly saw that holding Trấn Tây Thành was no longer worthwhile. It was like investing in a project that was increasingly losing money.
Thus, the Hue court began to consider withdrawal. But withdrawal did not mean abandoning everything. The Nguyen dynasty still wanted to maintain influence in Cambodia, just not through direct control anymore. From 1845, negotiations with Siam were conducted, lasting until 1847 when both sides reached an agreement. Cambodia was returned autonomy but had to endure a dual dependency, meaning it was dependent on both Vietnam and Siam. The Vietnamese army angrily withdrew from Nam Vang, the fortifications were left behind, and the Vietnamese officials gradually departed. The name Trấn Tây Thành was officially erased from the administrative map, marking the end of a great ambition.
However, this withdrawal process was not smooth. Some Vietnamese officials still stayed behind to supervise, and the Khmers still harbored many grievances from the years of oppression before. Even in the hearts of the Cambodian people, the memory of the Trấn Tây Thành period left a deep wound affecting the relations between the two countries later. This process shows that no matter how strong Đại Nam was, controlling a nation with its own identity caught between two great powers was an almost impossible task. This story of withdrawal is not only the end of Trấn Tây Thành but also a historical lesson about respecting the culture and autonomy of neighboring peoples.
Although the period of Trấn Tây Thành lasted only about 30 years, it left many marks in the history of Vietnam and Cambodia. For Vietnam, this was a period that demonstrated the strength and ambition of the Nguyen dynasty in expanding influence in Southeast Asia. For Cambodia, this was a difficult period. But not everything was negative. Many Vietnamese who migrated to Cambodia during this time formed a Vietnamese community in Cambodia that remains an important part of this country's society today. Conversely, Khmer culture also influenced Vietnam, especially in the South through food, customs, and even farming methods.
And speaking of Trấn Tây Thành, one cannot forget a few figures. Notably among them is Thoại Ngọc Hầu, or Nguyễn Văn Thoại, a talented general of the Nguyen dynasty. He was the commander who built the Vĩnh Tế canal, a project over 90 km long connecting Châu Đốc to Hà Tiên. At that time, there were no machines; everything was done by hand in swampy conditions, with harsh weather, and tens of thousands of people, both Vietnamese and Khmers, participated in building this canal. This project not only helped transport military supplies but also supported trade and irrigation. To this day, the Vĩnh Tế canal remains a symbol of the perseverance and talent of the ancient Vietnamese.
Another interesting story is about Queen Ang May, a female king of Cambodia who was brought to the throne by the Nguyen dynasty in 1834. Ang May was special because she was seen as a bridge between Vietnam and Cambodia. The Hue court chose her to rule with the hope of creating harmony between the two peoples. However, her life was also full of tragedy as she was caught in the political turmoil of the two countries. Nevertheless, Ang May's presence shows that the Nguyen dynasty also tried to find ways to reconcile, though not always successfully. Another interesting detail is the struggle for the throne in Cambodia at that time. The Cambodian kings and princes not only fought among themselves but were also caught between Vietnam and Siam. Each side supported a different candidate to be king, turning Cambodia into a political chessboard.