Although weapon-like tools and armor were found among the artifacts, the lack of battle fortifications found on the Minoan research sites suggests that the civilization was peaceful as a whole. There is very little evidence to suggest that there were ever any major internal disputes within the Minoan civilization, however there are several factors that are said to have influenced its later downfall. One of the most supported is the theory that it was due to outside conquest. Spyridon Marinatos, a Greek archaeologist, theorized that around 1500 B.C.E. a nearby volcano had erupted on the island of Crete, weakening the civilization. It likely did not cause the demise of the civilization but it crippled both its population and its economy making the Minoans vulnerable. Taking advantage of this weakness, the Mycenaeans, a neighboring military civilization, invaded the Minoans. The Minoans were not an aggressive military power but their island isolation made them difficult to be subdued, so the destruction caused by the volcano's eruption was enough to allow the Mycenaeans to successfully invade.