The Persians in the Age of Empires II are largely based on the Sassanid Persian Empire. The Persians as a culture existed for many centuries when the Middle Ages began. It had been reassembled following the conquest by Alexander in the fourth century BC and the subsequent breakup of his empire in later centuries. The Persians had been fighting the Romans since the third century AD.
The Persian Empire stretched from Mesopotamia to India and from the Caspian Sea to the Persian Gulf, encompassing the modern nations of Iraq, Iran, and Afghanistan. They fought the Romans, and later the Byzantines, for control of modern Syria, Turkey, Palestine, Israel, Egypt, and Arabia. The capital of the Persian Empire was Ctesiphon, called Baghdad today.
The Persians are a Cavalry oriented civilization. They have full cavalry tech and their team bonus allows them to do bonus damage to archers. Their unique unit is the War Elephant, a powerful but slow cavalry unit. It deals massive damage to all units and has a huge amount of Hit Points. This coupled with their powerful cavalry gives them powerful offensive capabilities. However their defense and infantry are somewhat weaker. They cannot build Fortified Walls and their towers are mediocre. In addition they are unable to research the Two Handed Swordsmen and Champion upgrades for their infantry units.