Around this period, Jayavarman II unified warring Khmer principalities and performed a consecration ceremony proclaiming himself a 'universal monarch,' free from any foreign overlord, atop the sacred mountain of Phnom Kulen. This act is traditionally dated to the year that later Khmer inscriptions used to mark the founding of the Angkorian era, the beginning of an empire that would eventually build Angkor Wat and dominate Southeast Asia for six centuries.
Much of what is known about Jayavarman II comes from a single inscription carved more than 300 years after his death, the Sdok Kok Thom stele, which describes a Brahmin priest performing a ritual to sever Cambodia's ties to 'Java'—likely referring to a rival Southeast Asian power rather than the island itself. The ceremony atop Phnom Kulen, a sandstone plateau considered sacred, established the devaraja cult that would underpin Khmer kingship for centuries, tying the ruler's legitimacy directly to Hindu cosmology and the god Shiva.
Jayavarman II's reign is frustratingly obscure by the standards of later, better-documented Angkorian kings; archaeologists still argue over the exact dates and details of his consolidation of power. Yet the tradition his ritual established proved extraordinarily durable, providing the ideological foundation on which his successors built an empire whose temples, reservoirs, and irrigation works at Angkor would eventually support a population rivaling any medieval city on Earth.
Within two centuries, Jayavarman II's line of god-kings had transformed a patchwork of competing Khmer chiefdoms into the dominant power of mainland Southeast Asia, culminating in Angkor Wat's construction under Suryavarman II in the 12th century. The precise date remains debated by historians, but 802 CE is the year most conventionally cited for Cambodia's founding as an independent, unified kingdom.