2,900 – 2,500 – The Dynastic Period
This period gets its name to describe the emergence of secular, hereditary, military kingdoms in Sumer. This political trend was accompanied by an increase in militarism and warfare. Fifteen to twenty Sumerian cities had grown more urban by concentrating themselves defensively. Kish and Erech had as many as 20,000 inhabitants. There was evidence of a class society: well to do, poor, and slaves.
There is much speculation about what caused the militancy: competition over scarce resources? Competition over unoccupied land? Lack of a buffer zone? War become chronic and kingships followed. Is this a history lesson?