What killed the Bronze Age?

Before 1177 BC there was a network of large, powerful nations like Egypt, Assyria, Minos and Troy trading. They'd survived for thousands of years but within a matter of decades all but one of those civilisations vanished and the sole survivor, Egypt, was irrevocably changed. Dr Eric Cline has spent his career picking through the rubble of ancient cities and his take on this highly controversial period of history is the subject of a new book 1177 BC: The Year Civilization Collapsed