Angkor is a name conventionally applie to the region of Cambodia serving as the seat of the Khmer empire that flourished from approximately the 9th century to the 15th century A.D. (The word "Angkor" itself is derived from the Sanskrit "nagara," meaning "city.") More precisely, the Angkorian period may be defined as the period from 802 A.D., when the Khmer Hindu monarch Jayavarman II declared himself the "universal monarch" and "god-king" of Cambodia, until 1431 A.D., when Thai invaders sacked the Khmer capital, causing its population to migrate south to the area of Phnom Penh.