Siamese-Vietnamese War (1841-1845)

The 1841-1845 Siamese-Vietnamese War in Cambodia was a war between Vietnam and Siam (Thailand), triggered by Siam's attempt to expand its influence in Cambodia and to prevent its rival, Vietnam, from territorial gains in the region at the expense of the declining Khmer Empire.

After the unsuccessful Siamese attempt to conquer Cambodia, Queen Ang Mey was installed on the Cambodian throne as her country increasingly came under the yoke of Vietnam. Vietnamese occupation caused a rebellion in 1841, with Cambodians massacring their Vietnamese masters and others, calling for aid from Siam, and supporting Cambodian prince Ang Duong (1796-1860) to return as king. King Rama III (d. 1851) of Siam sent an army in the name of returning Ang Duoung to the Cambodian throne in 1841. Having more than 50 forts in Cambodia, Vietnam waged a full-scale war that lasted for 4 years against rural insurgents and the Siamese, accepting defeat in general but refusing to withdraw from the country. This came to an end in 1845 when both sides agreed to a compromise peace, which placed Cambodia under joint Siamese and Vietnamese protection but with a Siamese predominance. In 1848, Ang Duong was officially crowned Cambodia's king.