Persia lost the battles of Granicus, Issus and Gaugamela, which led to Alexander's takeover of the Persian Empire.
It's takeover by Alexander the great.
It's takeover by Alexander the Great.
Invasion by an ambitious Alexander the Great who took over the Empire and turned it into an empire of his own.
Alexander the Great's 10 year military conquest was terminal.
The period of disorder after the decline of the Roman Empire led to an extended period of disunity during the Middle Ages that was characterized by feudalism.
It's takeover by Alexander the great.
It's takeover by Alexander the Great.
Invasion by an ambitious Alexander the Great who took over the Empire and turned it into an empire of his own.
Alexander the Great's 10 year military conquest was terminal.
The Persian Empire led by Cyrus.
Athens turned the Delian League which it had led against the Persian Empire into an empire of its own.
Athens turned the Delian League which it had led against the Persian Empire into an empire of its own.
Athens turned the Delian League which it had led against the Persian Empire into an empire of its own.
The period of disorder after the decline of the Roman Empire led to an extended period of disunity during the Middle Ages that was characterized by feudalism.
Athens converted the Delian League, which it had led against the Persian Empire, into an empire of its own.
The short answer is: infighting and the plague.
Athens, which turned the coalition of city-states it had led against the Persian Empire into an empire of its own.