Battle of Rạch Gầm-Xoài Mút

1785 battle fought in Vietnam between Tây Sơn forces and Siam

The Battle of Rạch Gầm Xoài Mút (, การรบที่ซากเกิ่ม สว่ายมุต) was fought between the Vietnamese Tây Sơn forces and an army of Siam in present day Tiền Giang Province on January 20, 1785. It is considered one of the greatest victories in Vietnamese history.

In the late 18th century, a rebellion broke out in southern Vietnam. The Nguyễn lords, the hereditary rulers in southern Vietnam, were overthrown by the Tây Sơn brothers: Nguyễn Nhạc, Nguyễn Huệ and Nguyễn Lữname=taysonsiamname in 1777. With the help of supporters, Nguyễn Ánhname=anhsiamname, a nephew of the last Nguyễn lord, reconquered Gia Định (present day Hồ Chí Minh City) as Đại nguyên súy Nhiếp quốc chính ("Commander in chief and regent") and later proclaimed himself Nguyễn Vương ("Nguyễn king"). In 1783 the Tây Sơn rebel forces recaptured Gia Định. Nguyễn Ánh had to flee to Phú Quốc island, while his army was attacked and defeated by a Tây Sơn army. One of Ánh's generals, Châu Văn Tiếp, was sent to Siam to make a request for aid. According to Vietnamese records, an army under the Siamese general Thát Xỉ Đa (撻齒多, also known as Chất Si Đa) arrived in Hà Tiên the next year. Nguyễn Ánh retreated to Siam with him, where they met king Rama I, who promised that Siam would support Ánh's struggle for dominance in Vietnam. There was an episode only mentioned in the Royal Thai Chronicles. In 1783, a Siamese army under Phraya Nakhonsawan (พระยานครสวรรค์) had marched to Cambodia to come to the aid of Nguyễn Ánh. There they clashed with Vietnamese forces of Ong Tin Wuang (องติเวือง, Nguyễn Lữname=taysonsiamname) in Sadec (Sa Đéc) and captured warships, prisoners and various types of weapons, yet later returned them to the Tay Son. A number of generals, Phraya Wichitnarong (พระยาวิชิตณรงค์) among them, disapproved the decision and secretly reported to Bangkok. Charged with treason Phraya Nakhonsawan and 12 men were executed in the graveyard of Photharam Temple in Ayutthaya. The Siamese Cambodian infantry contingents under Phraya Wichitnarong attacked Sa Đéc (Piamchopsadaek), where they defeated several Tay Son detachments. Phraya Wichitnarong then marched toward to Ba Lai (Piambarai) and attacked a Tay Son army in Ban Payung (Ba Giồng). However, the Siamese invaders met increasing resistance from the Tây Sơn army. Trương Văn Đa fought bravely against the Siamese invaders. On November 30, he defeated the Siamese Nguyễn fleet, killed Châu Văn Tiếp (the highest commander of the Nguyễn fleet) and wounded the Siamese general Thát Xỉ Đa at the Mân Thít River. Lê Văn Quân succeeded Tiếp as the highest commander of the Nguyễn fleet. By the end of 1784, the Siamese had taken Rạch Giá, Trấn Giang (Cần Thơ), Ba Thắc (Srok Pra sak, Sóc Trăng), Trà Ôn, Sa Đéc, Mân Thít (or Mang thít, Man Thiết), and controlled Hà Tiên, An Giang and Vĩnh Long. But important places, including Mỹ Tho and Gia Định, were still controlled by the Tây Sơn army. Realizing he was unable to repulse the enemy, Trương Văn Đa sent Đặng Văn Trấn to Quy Nhơn for help.

The Tây Sơn reinforcements led by Nguyễn Huệname=taysonsiamname marched south from Quy Nhon and arrived in Cochinchina territory around January 1785. Huệ set up his headquarter in Mỹ Tho, not far from Trà Tân, the headquarter of the Siamese troops. Small groups of Tây Sơn navy harassed Siamese fortified points during high tide and withdrew during low tide. They gathered intelligence about the Siamese navy and pretended to be vulnerable. After many victories, the Siamese army and naval forces were overconfident. One of the secret weapons of the Tây Sơn force was the Hỏa Hổ Thần Công (Flaming Tiger Cannon), which could release a stream of fire at a very long range. The battle ended with a near annihilation of the Siamese force, as according to Vietnamese sources all the ships of the Siamese navy were destroyed.