Founding

Khmer tradition and inscriptions date the empire to 802 AD, when Jayavarman II was consecrated chakravartin — universal ruler — on the Kulen hills, declaring independence from Javanese overlordship. His successors settled the capital region on the plain north of the Tonlé Sap lake: Angkor, which would be rebuilt, temple by state temple, by nearly every reign for six centuries.

The hydraulic city

Angkor’s power was water management: enormous reservoirs (barays), canals, and embankments that banked the monsoon against the dry season and fed rice systems supporting, at the 12th-13th-century peak, a low-density conurbation lidar surveys now put at roughly 1,000 square kilometres — the largest settlement complex of the pre-industrial world. Suryavarman II raised Angkor Wat in the early 12th century as a Vishnu temple aligned to his own funerary cult — still the largest religious structure on Earth. After a Cham sack in 1177, Jayavarman VII rebuilt in colossal Mahayana Buddhist idiom: the walled city of Angkor Thom and the face-towered Bayon, plus highways, rest-houses, and — his inscriptions boast — over a hundred hospitals. The Chinese envoy Zhou Daguan, resident in 1296-97, left the sole eyewitness account of the living city: gilded processions, floating festivals, and the king dispensing justice from a golden window.

Transformation

From the 14th century the empire contracted. Tree-ring climate records reveal decades-scale megadroughts punctured by violent flood years that wrecked the ageing water network; excavations show canals choked and breached. Theravada Buddhism, spreading from Sri Lanka, dissolved the temple-economy that mobilised Angkor’s labour; trade gravitated toward the Mekong and the sea; and the rising Siamese kingdom of Ayutthaya pressed from the west, sacking Angkor in 1431. By mid-century the court had shifted toward the Phnom Penh region — though Angkor Wat itself never ceased to function as a Buddhist shrine.

The Khmer state continued at reduced scale into the colonial era; the empire’s monuments, canals, and Sanskrit-and-Khmer inscriptions remain Cambodia’s foundation — Angkor Wat has appeared on every Cambodian national flag since 1863.