The Hittite Empire eventually collapsed following invasion from the west by the Achaeans, the Phrygians, and a mysterious force known only as the  Sea People.  
The Hittite Empire finally collapsed due to invasion.
mnli hypothesis: The Hittite Empire finally collapsed due to invasion. premise: The Hittite Empire eventually collapsed following invasion from the west by the Achaeans, the Phrygians, and a mysterious force known only as the  Sea People.  