Complex sentence: Helped by Akhenaten's apparent lack of interest in international affairs, the Hittites had gradually extended their influence into Syria and Palestine to become a major power in international politics, a power that both Seti I and his son Ramesses II would need to deal with.
Split into simpler sentences: Helped by Akhenaten's apparent lack of interest in international affairs, the Hittites had gradually extended their influence into Syria and Palestine to become a major power in international politics. A power that both Seti I and his son Ramesses II would need to deal with.