Tân An in the context of Tây Ninh Province

Tây Ninh (listen) is a formerly provincial city in Southeastern Vietnam. The new provincial capital is located in Long An Ward, Tây Ninh Province (formerly as Tân An City, Long An Province). Tây Ninh is one of nine provinces and cities in the Southern Key Economic Region (Ho Chi Minh City metropolitan area). Tây Ninh is approximately 90 km (55 miles) northwest of Ho Chi Minh City, the largest city of Vietnam, and 182 km (113 miles) to Phnom Penh, capital of Cambodia; all by National Route 22. As of 2019, the city had a population of 135,254 over the provincial population of 1,169,165 on a total area of 140 km (54 sq mi).

Nguyễn Phúc Khoát (26 September 1714 – 7 July 1765) was one of the Nguyễn lords who ruled over the southern portion of Vietnam from the 16th-18th centuries. Also known as Chúa Võ (主武) or Võ vương (武王) (roughly Martial King), he continued the southern expansion undertaken by his predecessor, Nguyễn Phúc Trú. Provinces and districts originally belonging to Cambodia were taken by Khoát. The Vietnamese-Cambodian border established by the end of his reign remains the border today. The de jure pretense of loyalty to the Lê dynasty was performed by Khoát.

In 1747, Khoát sent a number of Vietnamese warriors to aid rebel princes of Cambodia against the newly crowned Cambodian King Ang Tong. These forces seized Sóc Trăng town and then moved towards Oudong, then royal capital of Cambodia. Ang Tong requested aid from Mạc Thiên Tứ, who secured a truce with the Nguyễn lord, in exchange for a few more provinces, namely Gò Công and Tân An. Ten years later, the Cambodian throne was seized by Outey II, with the help of Nguyễn and Mạc. In return for their contributions, he granted them seven provinces, including Sóc Trăng, Trà Vinh, Kampot, and Kompong Som.