The growth of the Persian Empire under Cyrus, Cambyses, and Darius.
Persians first settled on the plateau of Iran (that is the present territory of Persia) several thousand years ago. The first evidence of them appears in Assyrian inscription of the ninth century BC. But the history of Persia as a great nation began in the sixth century BC when Cyrus united the various Persian tribes and defeated the neighboring peoples, thus building a large empire.
Persian history can be divided into two main periods. The first period starts with the age of Cyrus and goes on until the Arab conquest in AD 651; the second begins in the year AD 651 and goes on until the present time. In the second period Persia/Iran has been a Moslem country.