The Bronze Age at its height witnessed several large empires and peoples in regular contact with one another through both trade and war. The pharaohs of the New Kingdom corresponded with the kings and queens of the Hittite Empire and the rulers of the Kassites and Assyrians; it was normal for rulers to refer to one another as “brother” or “sister.” Each empire warred with its rivals at times, but it also worked with them to protect trade routes. Certain Mesopotamian languages, especially Akkadian, became international languages of diplomacy, allowing travelers and merchants to communicate wherever they went. Even the warlike and relatively unsophisticated Mycenaeans played a role on the periphery of this ongoing network of exchange.
That said, most of the states involved in this network fell into ruin between 1200 - 1100 BCE. The great empires collapsed, a collapse that it took about 100 years to recover from, with new empires arising in the aftermath. There is still no definitive explanation for why this collapse occurred, not least because the states that had been keeping records stopped doing so as their bureaucracies disintegrated. The surviving evidence seems to indicate that some combination of events - some caused by humans and some environmental - probably combined to spell the end to the Bronze Age.
Around 1050 BCE, two of the victims of the collapse, the New Kingdom of Egypt and the Hittite Empire, left clear indications in their records that drought had undermined their grain stores and their social stability. In recent years archaeologists have presented strong scientific evidence that the climate of the entire region became warmer and more arid, supporting the idea of a series of debilitating droughts. Even the greatest of the Bronze Age empires existed in a state of relative precarity, relying on regular harvests in order to not just feed their population, but sustain the governments, armies, and building projects of their states as a whole. Thus, environmental disaster could have played a key role in undermining the political stability of whole regions at the time.
Even earlier, starting in 1207 BCE, there are indications that a series of invasions swept through the entire eastern Mediterranean region. The New Kingdom of Egypt survived the invasion of the “sea people,” some of whom historians are now certain went on to settle in Canaan (they are remembered in the Hebrew Bible as the Philistines against whom the early Hebrews struggled), but the state was badly weakened in the process. In the following decades, other groups that remain impossible to identify precisely appear to have sacked the Mycenaean palace complexes and various cities across the Near East. While Assyria in northern Mesopotamia survived the collapse, it lost its territories in the south to Elan, a warlike kingdom based in present-day southern Iran.
The identity of the foreign invaders is not clear from the scant surviving record. One distinct possibility is that the “bandits” (synonymous in many cases with “barbarians” in ancient accounts) blamed for destabilizing the region might have been a combination of foreign invaders and peasants displaced by drought and social chaos who joined the invasions out of desperation. It is thus easy to imagine a confluence of environmental disaster, foreign invasion, and peasant rebellion ultimately destroying the Bronze Age states. What is clear is that the invasions took place over the course of decades - from roughly 1180 to 1130 BCE - and that they must have played a major role in the collapse of the Bronze Age political and economic system.
For roughly 100 years, from 1200 BCE to 1100 BCE, the networks of trade and diplomacy considered above were either disrupted or destroyed completely. Egypt recovered and new dynasties of pharaohs were sometimes able to recapture some of the glory of the past Egyptian kingdoms in their building projects and the power of their armies, but in the long run Egypt proved vulnerable to foreign invasion from that point on. Mycenaean civilization collapsed utterly, leading to a Greek “dark age” that lasted some three centuries. The Hittite Empire never recovered in Anatolia, while in Mesopotamia the most noteworthy survivor of the collapse - the Assyrian state - went on to become the greatest power the region had yet seen.