During the second and early first millennia b.c., the Middle Eastern empires of domination were shaken by two immense challenges, which appeared external and yet which they had stimulated. Most empires did not survive – some vanished, and others were incorporated as units into others' dominions – and those that did survive were profoundly changed by the challenge into “world empires,” self-styled. The two challenges were the military dominance of charioteers between about 1800 and 1400 b.c. and the spread of iron weapons and tools from about 1200 to 800 b.c. These revolutions had three similarities: They emanated from the north, from no settled peoples, and from no literate peoples. These facts create difficulties for our analysis, for we need to shift to areas whose precise location is unknown and to peoples who at first left few remains and records. In these circumstances it is difficult to avoid the mistake passed to us by the empires themselves, that these events constituted “sudden eruptions” of barbarism and catastrophe.

But the real story is not one of the clash of two separate societies. In this period the unitary model of society bears little relationship to reality. What happened is explicable in terms of (1) the initial stimulus given by the Near East to a steadily widening geographical area and to the diverse power networks contained there and (2) a subsequent growth in the extent of overlapping, intersecting power interactions within this area.