Tây Sơn military tactics and organization

There were 673 ships and vessels that had been accounted for, run by 53.250 marine soldiers under the command of admiral Vũ Văn Dũng.[4][5] Large vessels served to carry troops, food and equipment, as the light and flexible boats were used for actual combat.

Model of a Tay Son warship, currently on display at the Tay Son Museum (Binh Dinh, Vietnam). This is a large ship with strong firepower at that time.

The Type-4 battleship and Type-5 battleship were small but easy to handle and very useful for riverine combat. Equipped with oars, its crews were trained in river navigation and long distance troop transportation.

In 1788, Nguyễn Huệ parted forces with Nguyễn Nhạc, and left South Vietnam in response to an attack of Chinese imperial troops. He organized a naval transport for General Bảo to deal with an increasingly drastic situation.

Laurent André Barisy, a French naval officer in Nguyễn lords service, reported on the forces of the Tây Sơn fleet led by Vũ Văn Dũng as follows:

"This force consists of 673 vessels, that include large warships armed with cannon and crew comparable to the largest Western-style warships of Nguyễn Ánh."

Jeaptiste Chaigneau, in Quy Nhơn, states in a letter, that the Tây Sơn navy had 54 battleships, 93 battleboats, 300 gunboats, and 100 sailing boats.

In a letter to Letondal on April 11, 1801, concerning the naval Battle of Thị Nại, Barizy states that the Tây Sơn navy had 4,800 transport boats in the Thị Nại harbor.

During the Tây Sơn army advance in preparation of the clash with the Siamese army, Nguyễn Huệ avoided suspicious resting places like Gia Định and camped his force in Mỹ Tho, in order to conceal the conduct of his forces a much as possible. He carefully scouted and reconnoitered the situation and waited for a surprise confrontation with the completely exposed enemy.

For the battle of Rach Gam-Xoai Mut, Nguyễn Huệ chose a section of the Mỹ Tho river, in between Rạch Gầm river and Xoài Mút river to confront the Siamese troops. The two small rivers Rạch Gầm and the Xoài played an important part in the plan of Nguyễn Huệ, as the Tây Sơn infantry could be deployed there and block the Siamese navy on the river. At the mouth of the Rạch Gầm and the Xoài Mút river are the Thới Sơn Island and the Hộ island, a convenient place that was chosen to secretly deploy artillery, attack the enemy and easily pick up isolated Siamese detachments, that landed on the shore. The rivers between the islands served as base and ambush stage for the Tây Sơn navy, that was instructed to draw enemy ships into confined areas and single them out where it was easier to deal with them.[8]

One of the most unconventional Tây Sơn tactics was to conduct combat operations during the middle of the night and disengage before dawn. The Tây Sơn troops would spend the day hidden in secret shelters and only struck again, when the situation was advantageous for successful combat.[9]

During their first campaign in Northern Vietnam, the Tây Sơn navy was besieged by Trịnh Khải's navy on the Vị Hoàng river. Under the guise of heavy winds, Nguyễn Huệ sent some ships with wooden troop decoys and under full banners to approach the enemy while they still beating the drums. The Trịnh army commander Đinh Tích Nhưỡng believe that, so him order all guns of Trịnh army fire, until exhausted gun shot, he realized Tây Sơn's deception. Eventually, when Nguyễn Huệ's troops suddenly rushed in to fight, the Trịnh forces did not resist and just abandoned their boats and run away. Other Trịnh lord army divisions were also destroyed and the Sơn Nam citadel was demolished.[10]

On December 20, 1788, Tây Sơn reinforcements under the command of Nguyễn Huệ (who was by then Quang Trung emperor) advanced to the Tam Điệp mountains. His generals Ngô Văn Sở, Ngô Thời Nhiệm and Phan Văn Lân, they are apology their mistake, cause suddenly withdrawal when the Qing army attacked Thăng Long. Quang Trung smiled:

"Withdrawal to evade the enemy in their time overflowing power, encourages general morale, and builds arrogance in the enemy force, luring the enemy into our trap. That way is good. You all (Quang Trung's generals) have made no mistake. They have come here (Đại Việt) to buy death, and I am going to give it to them." ("Lui quân để tránh thế giặc, trong khuyến khích tướng sĩ, ngoài làm cho giặc phấn khích, kiêu ngạo, dụ địch vào chỗ hiểm yếu của ta như thế là phải. Các khanh không có tội chi cả. Chúng nó sang đây là mua lấy cái chết đó thôi, ta đã định mẹo cả rồi".)[10]

To make more arrogant in the Qing army, Quang Trung make an order to Trần Danh Bình lead a group eight people, they carried gifts and letters to Sun Shiyi conjured him stop his troops, and listen to understand clearly reasons: "why Tây Sơn had to subvert Lê dynasty". And they also returned to Sun Shiyi 40 Chinese mans. All man was captured by Đắc Thiện Tống pirates commander, after that time, Tây Sơn troops captured him. But Sun Shiyi was beheaded both Trần Danh Bình, and Đắc Thiện Tống. Kept in all messengers to prison. During this time, Quang Trung secret to preparing attack, deciding a plan to kick Qing enemy inside Đại Việt get out their territory. On the morning of December 30, before begin attack, Quang Trung said:

"We came to enemy place, they do not know when they sleeping but we awake, we hit the enemy not in case that mean we massacre the enemy in empty hand, we definitely win..." ("Ta đến mà địch không biết là địch ngủ ta thức, ta đánh mà địch không đề phòng là ta chém kẻ tay không. Ta nhất định thắng...")

That secret factors, the Qing army did not clear the strength of the Tây Sơn, and more disdain, so when Qing army under attack they can not repulse Tây Sơn army.

Preparations for the Battle of Rach Gam-Xoai Mut very well illustrate to how deep Nguyễn Huệ's tactical plannings went. In advance he sent field observers to study and fully understand the laws and tidal phases of river, the characteristics of channels, creeks, estuaries and the terrain on both river banks. He deployed selected forces in the area in advance. In accord with the order of deployment for the elite naval forces, he arranged the most effective concentration of artillery and mobile troops on both sides, ready to attack the front and the rear of Siamese forces, that entered the combat zone. The Tây Sơn also had been trained to carry out combined maneuvers of the navy forces in the rivers, creeks and branches and the infantry, operating on the river banks and the surrounding ground.[11]

The French Clergyman Le Breton wrote in a letter on August 2, 1788: "As it happened Nguyen Hue returned to Phu Xuan in early July. He had rushed his troops so fast that many of his soldiers died of fatigue and heat. Even the elephants and horses, they died too."

According to Nguyễn Huệ's own account he once led an infantry and cavalry contingent in a 10 days march from Phú Xuân to Thăng Long in order to catch and execute Vũ Văn Nhậm. The reliability of this remarkable feat is supported by an entry in the Diary of the Bac Ha Missionary Church. The report on the strength of the Quang Trung emperor sent to the Central Church reads: "He (Nguyen Hue) moved like a hurricane to the North that only took 10 days, the long distance has killed many of his elephants and horses after 3 to 4 days." A distance of more than 600 km (372.82 mi) as roads traverse mountains and cross rivers, in a 10 days march with such a large army is extraordinary. Horses and elephants dropped dead along the road. Nguyen Hue applied his principle of collective, continuous day and night move. He had his troops form teams of three, that rotated with each other, as on the march two people shielded the third person.[12]

Not only did attack speed,[13] Quang Trung's twin tactic was to attack suddenly, to strike at unbelievable times, preventing their defenses from leading to defeat.[9]

In the offensive in 1786, while the commander of Trịnh army was out of alert, the Tây Sơn troops began their journey on 28 April lunar month, that 25 May 1786.[14] In the middle of the fifth lunar month of 1786, Tây Sơn's army lead by Nguyễn Huệ make a surprise attack, the Trịnh army failed to turn up. Hoàng Nghĩa Hồ rescued his troops and was killed.[15] To capture Hải Vân, Nguyễn Huệ immediately forward troops to Phú Xuân. The second time, the Trịnh troops surprise. Trịnh Tông concentrated in the Tây Long fort, there were 100 war elephants,[15] totaling 30.000 Trịnh troops on Thăng Long defense. In the critical situation known to be attacked, Trịnh was still not alert, suggesting that the Tây Sơn troops could not advance to Thăng Long quickly.[16] Eventually, the Trịnh lordship collapsed.

On December 20, 1789, Tây Sơn troops came to Ninh Bình. After reviewing the situation, Quang Trung told his soldiers that in just 10 days, Qing army would be cleaned up. Qing army and Lê Chiêu Thống are in preparation for the Tết holiday, which is not well protected, plus Sun Shiyi's arrogance makes them really surprised. Soon, within six days of the Lunar New Year, the Tây Sơn troops destroyed the Qing army. At 5th Lunar New Year in 1789, Tây Sơn troops entered Thang Long. Sun Shiyi warriors run away, on the road running successively defeated by Tây Sơn soldiers. Finally, Sun Shiyi and Lê Chiêu Thống run away to China.

The Tây Sơn used Psychological warfare to gain the support of the masses and the youth to join the army. First of all, in the new stage of setting up the Tây Sơn uprising against Trương Phúc Loan to support Nguyễn lords. So that, they was have belief of lord and many people.

In the later stage, using the name "Phù Lê diệt Trịnh", Nguyễn Huệ talk Nguyễn Hữu Chỉnh moved to the North. Trịnh lords lost on the battlefield, hate by many people in North Vietnam, Trịnh Tông to run out Thang Long, the people touch him and brought to submit Tay Son. Finally, Trịnh Tông suicide.

Vietnamese language:

• Khâm định Việt sử Thông giám cương mục.
• Nguyễn Lương Bích, Phạm Ngọc Phụng (1976), Tìm hiểu thiên tài quân sự của Nguyễn Huệ, Quân đội Nhân dân Publishing House.
• Nguyễn Việt – Vũ Minh Giang – Nguyễn Mạnh Hùng (1983), Quân thủy trong lịch sử chống ngoại xâm, Quân đội Nhân dân Publishing House.
• Trần Trọng Kim (1920), Việt Nam sử lược, Tân Việt Publishing House, ed.1968.
• Vietnam Institute of History, Quang Trung Nguyễn Huệ với chiến thắng Ngọc Hồi-Đống Đa, Quân đội Nhân dân Publishing House, 1992.