After the peak of Jayavarman VII’s rule, Angkor entered a gradual decline, with many territories in what is now Thailand, such as Sukothai and Louvo, reclaiming their independence. A resurgence of Thai forces eventually led to a series of invasions, culminating in the capture and sacking of Angkor in 1431, traditionally marked as the empire’s fall.

While the Thai incursions are often seen as the main cause of Angkor’s downfall, the true reasons were likely more complex and unfolded over a long period. The constant outflow of resources devoted to temple construction may have strained the kingdom, as did the rising influence of Theravada Buddhism, which opposed the god-king traditions that had dominated Angkor. Yet, the most probable root cause of the city’s eventual collapse was ecological. Rapid population growth led to widespread deforestation, diminishing soil fertility, and causing silt buildup in the sophisticated water management systems. Stagnant canals and reservoirs eventually became breeding grounds for malarial mosquitoes, posing a serious health risk to the population.

Despite these challenges, Angkor persisted for a time. In 1570, Dominican friar Gabriel Quiroga de San Antonio visited and observed the city still active and relatively prosperous, suggesting that its decline, while inevitable, was a slow process influenced by multiple interconnected factors.