Fall of Angkor (1431)

The fall of Angkor refers to the capture and looting of the Khmer capital at Angkor by the Ayutthaya Kingdom, an event conventionally dated to 1431. According to Thai chronicle traditions, Angkor Thom was besieged for roughly seven months, beginning in 1430 and ending with the city's capture the following year. This 1431 episode followed two earlier periods of Siamese occupation of Angkor, in 1352–1357 and 1393–1394, each involving sieges, the installation of vassal rulers, and the removal of captives and wealth to Ayutthaya.

In the 1431 episode, Angkor was sacked by the Siamese king Borommarachathirat II. Accounts describe Khmer king Ponhea Yat subsequently leading a large force to retake Angkor, including a covert operation in which disguised agents were sent into the Angkor royal palace to kill the Siamese ruler then controlling the city. Following the recovery of the city, Ponhea Yat is described as resuming his reign under the title "Preah Barom Reachea." Because Angkor's treasures had been taken and the city, including its walls, had suffered significant damage requiring costly repair, and to reduce the risk of further Siamese attack, the Khmer court relocated the capital, first to Tuol Basan (Srey Santhor) and later, after a serious flood at Tuol Basan, to the Chaktomuk area, now part of Phnom Penh. This relocation is often used to mark the beginning of the Post-Angkor period.

Historians attribute the fall of Angkor to a combination of human and natural factors, and debate over their relative weight continues. Human factors discussed include the 1431 Siamese military campaign itself; the possibility that Champa forces raided the city for its wealth; the collapse of Angkor's hydraulic water-management system amid ecological strain from expanded irrigated rice cultivation into forested land; Malthusian pressure from population growth outstripping food supply; and a proposed "crisis of faith" linked to the Khmer Empire's shift toward Theravada Buddhism after the reign of Jayavarman VII, which some scholars argue eroded the Hindu concept of divine kingship underpinning Angkorian civilization and the associated large temple-maintenance workforce. Natural factors cited include a severe Southeast Asian drought in the early 1400s, associated with a weakened East Asian summer monsoon, which may have dried out Angkor's reservoirs and canals, and broader climate change during the transition from the Medieval Warm Period to the Little Ice Age.

Despite the political relocation, archaeological and inscriptional evidence, including the Grande Inscription d'Angkor, indicates that major Angkorian temple sites were not abandoned outright; they continued to be used for Theravada Buddhist worship, with Khmer royalty periodically returning to restore statues and pay respects. The period following the fall of Angkor is characterized by limited surviving documentation, and no Cambodian literature can be precisely dated to the 15th or 16th centuries, with many Khmer writers and books said to have been relocated to Siam and Sanskrit inscriptional use giving way to Middle Khmer.