Attacks on and conquests of Khmer royal residences left sovereigns without a ceremonial and legitimate power base.
Ambiguous fortunes, a robust economy on the one hand and a disturbed culture and compromised royalty on the other were constant features of the Longvek era.
By the 15th century, the Khmers' traditional neighbours, the Mon people in the west and the Cham people in the east had gradually been pushed aside or replaced by the resilient Siamese/Thai and Annamese/Vietnamese, respectively.
These powers had perceived, understood and increasingly followed the imperative of controlling the lower Mekong basin as the key to control all Indochina.
A weak Khmer kingdom only encouraged the strategists in Ayutthaya (later in Bangkok) and in Huế.
A new dynasty of provincial origin introduced Buddhism, which according to some scholars resulted in royal religious discontinuities and general decline. Great achievements in administration, agriculture, architecture, hydrology, logistics, urban planning and the arts are testimony to a creative and progressive civilisation - in its complexity a cornerstone of Southeast Asian cultural legacy.
The decline continued through a transitional period of approximately 100 years followed by the Middle Period of Cambodian history, also called the Dark ages of Cambodia, beginning in the mid 15th century.