Complex sentence: Throughout the 1350s Ayutthaya expanded over western Khmer territories and the Khorat Plateau, in 1352 Angkor was attacked in a failed attempt to take the capital.
Split into simpler sentences: Throughout the 1350s Ayutthaya expanded over western Khmer territories and the Khorat Plateau. In 1352 Angkor was attacked by Ayutthaya in a failed attempt to take the capital.