Original sentence: After Ang Chan II (1791-1837) retook the Cambodian throne in 1812, Siamese forces moved into northern Cambodia and then southward in support of their own claimant to the throne
Edited sentence: After Ang Chan II (1791-1837) retook the Cambodian throne in 1812, from the rightful ruler, Siamese forces moved into northern Cambodia and then southward in support of their own claimant to the throne