The Late Bronze Age collapse was a time of widespread societal collapse during the 12th century BC associated with environmental change, mass migration, and the destruction of cities. The collapse affected a large area of the Eastern Mediterranean (North Africa and Southeast Europe) and the Near East, in particular Egypt, eastern Libya, the Balkans, the Aegean, Anatolia, and, to a lesser degree, the Caucasus. It was sudden, violent, and culturally disruptive for many Bronze Age civilizations, and it brought a sharp economic decline to regional powers, notably ushering in the Greek Dark Ages.
https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse