The Parthians have expanded from their homelands south of the Caspian sea and now rule one of the great states of the ancient world, covering Iran and Mesopotamia. They are treated as an equal power by Rome, whom they defeated in a decisive battle at Carrhae in 54 BC.
The Parthian empire is frequently troubled by central Asian nomads from the north east, but they have developed effective defences against them. The Parthians themselves originated as central Asia nomads, but once established as the rulers of agricultural lands, they bred heavier horses and have developed an excellent cavalry that can out-fight the steppe horsemen on their smaller ponies. This cavalry is dispersed throughout the border regions as a military aristocracy. With its most effective military arm thus deployed along the northern frontier, Parthia is not usually geared up for major aggressive campaigns against its powerful neighbour, Rome.