One of the biggest mysteries in history is the late Bronze Age Collapse. There's no good explanation for why an early globalized civilization should suddenly disappear at around 1177 BC. "Within a period of forty to fifty years at the end of the thirteenth and the beginning of the twelfth century almost every significant city in the eastern Mediterranean world was destroyed, many of them never to be occupied again."
Modern archaeologists have advanced a number of theories to explain this catastrophe, several of which will sound familiar to modern ears. Climate change -- not the anthropogenic kind, since "fossil fuels" had not yet been developed -- might have caused drought and starvation. A technological revolution caused by the replacement of bronze with iron could have destabilized the international system. Perhaps the most modern-sounding of all explanations is "complexity." The interdependence fostered by trade left the linked empires open to a general systems collapse as the failure in one place unleashed a cascade of effects in others:
The growing complexity and specialization of the Late Bronze Age political, economic, and social organization in Carol Thomas and Craig Conant's phrase together made the organization of civilization too intricate to reestablish piecewise when disrupted. That could explain why the collapse was so widespread and able to render the Bronze Age civilizations incapable of recovery.
The critical flaws of the Late Bronze Age are its centralization, specialization, complexity, and top-heavy political structure. These flaws then were exposed by sociopolitical events (revolt of peasantry and defection of mercenaries), fragility of all kingdoms (Mycenaean, Hittite, Ugaritic, and Egyptian), demographic crises (overpopulation), and wars between states. Other factors that could have placed increasing pressure on the fragile kingdoms include piracy by the Sea Peoples interrupting maritime trade, as well as drought, crop failure, famine, or the Dorian migration or invasion.
Eric Cline, professor of ancient history at The George Washington University, believes the collapse was caused not by a single factor but by all of the above. Cline called it "the perfect storm" in his YouTube lecture. In the published summary of his book 1177 BC on Amazon, the precis puts it this way:
The end was brought about by multiple interconnected failures, ranging from invasion and revolt to earthquakes, drought, and the cutting of international trade routes. Bringing to life the vibrant multicultural world of these great civilizations, he draws a sweeping panorama of the empires and globalized peoples of the Late Bronze Age and shows that it was their very interdependence that hastened their dramatic collapse and ushered in a dark age that lasted centuries.
Interest in the Bronze Age collapse is fueled no doubt by fears that our own civilization may meet the same fate. A 2017 BBC article exploring ways our current civilization could fail warns against dangers roughly analogous to those which brought down the world of Troy. Those factors cited are: