27 BCE – 235 CE
Roman Empire (mature)
Centralized, tax-extractive, military-bonded. Stability through standing legions and a transport network covering the Mediterranean. Cultural cohesion via citizenship grants and lingua franca.
End mechanism
Élite overproduction → civil wars (235–284). Currency debasement → economic erosion. Frontier tax base shrunk; Western half could no longer sustain its complexity.