Bronze Age Collapse

The Late Bronze Age Collapse was a total systems collapse in the Eastern Mediterranean happening in ~1200 - ~1150 BCE. It manifested in the destruction or abandonment of most cities in the region, a huge decline in literacy, the collapse of centralized states, and the stop of global trade, all of this happening at roughly the same time. This mostly affected the regions of Greece, Crete, Cyprus, Anatolia, Levant, and finally Egypt (so the Mycenaean confederation, and the Hittite and Egyptian empires). However, the effects were felt by civilizations further east as well, including Assyria, Babylonia, Elam, and even the Indus Valley, and they suffered too because of this, though not as drastically as the Eastern Mediterranean civilizations.

Not enough characters to explain it in detail but TL;DR:
1) Plague + droughts + earthquakes and volcanic eruptions
2) Internal rebellions + barbarian invasions
3) Collapse of states
4) Sea Peoples
5) Collapse of more states
6) No trade
7) Collapse of the rest
8) Dark ages.