tl;dr: The Late Bronze Age Collapse (c. 1220–1170 BC) was a wave of site destructions and state failures across the Eastern Mediterranean and Near East, hitting Mycenaean Greece and the Hittite Empire hardest while Egypt, Assyria, and Babylon declined but survived. The likely cause was a combination of factors—drought-driven harvest failures, intensifying warfare straining centralized palace economies, and cascading disruptions from refugees/raiders (the "Sea Peoples")—rather than any single cataclysm or migration like the debunked "Dorian Invasion." The aftermath saw Greece deurbanize and lose writing entirely, but the resulting fragmentation enabled the rise of the Phoenicians, the Greek polis, and the kingdoms of Israel and Judah.