Alexander the great took over the Empire.
The breakaway of the Greek city-states of Asia Minor, the rise of Macedonia and its conquest of Persia.
The Persian Empire.
The Persian Empire was not a person.
Persian Empire
The Persian Empire absorbed the Baabylonian Empire.
Their loss in the Greco-Persian War as well as internal unrest within conquered lands.
The breakaway of the Greek city-states of Asia Minor, the rise of Macedonia and its conquest of Persia.
Internal revolution, including by the Greek city-states and Egypt. The threat and then actuality of invasion by Macedonia.
The Persian Empire.
The Persian Empire was not a person.
Persian Empire
The Persian Empire absorbed the Babylonian Empire.
Alexander the Great defeated the Persian empire
Egypt was conquered by Cambyses II, the ruler of the Achaemenid Empire, the second of the four pre-Islamic Persian Empires
The Persian Empire absorbed the Baabylonian Empire.
The Persian Empire incorporated the Indus Valley.
Alexander conquered the Persian Empire.