Scholars frequently assert that the decline of the Khmer Empire was precipitated by the drain on its economy, and on the morale and energy of its people, caused by the continual and monumental construction program at Angkor. Dynastic rivalries took their toll, and slave rebellions are also thought to have hastened the demise of the empire.
Over the centuries, the Khmer kings never completely pacified the countryside. Khmer martial spirit survived, as was demonstrated by uprisings and rebellions, either spontaneous or contrived, throughout periods of foreign encroachment and domination. Among the significant rebellions was one that occurred beginning in 1840 which resulted in Cambodia's being placed under the joint suzerainty of Thailand and Vietnam (see Domination by Thailand and Vietnam, ch. 1).
Data as of December 1987