Complex sentence: Many of the existing cities began--or were compelled by force--to adopt Hellenized philosophic thought, religious sentiments, and politics although the Selecuid rulers did incorporate Babylonian religious tenets to gain support.
Split into simpler sentences: Many of the existing cities began--or were compelled by force--to adopt Hellenized philosophic thought, religious sentiments, and politics. Although, the Selecuid rulers did incorporate Babylonian religious tenets to gain support.