The 10,000 Immortals as its core, and, most importantly, the cavalry.
The Macedonians under Alexander defeated a provincial Persian army, allowing Alexander to continue his advance into the heart of the Persian Empire.
Alexander the Great defeated the Persian empire
The Persians would have won if Sparta and Athens had not united to fight the Persian Army
The strong army that Alexander defeated was the Persian Army
Being outmanoeuvred by Alexander the Great - who first slaughtered Greeks who were bolstering up the Persian army, then putting an end to the Persian fleet by occupying their bases in the Mediterranean, then capturing the Persian treasury which enabled him to pay his army, and inflicting a final land defeat of the Persian army.
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Who is 'you do'.
The Persian army and a much smaller army made up of combined forces from the city-states of Greece.
The small Greek force at Thermopylae was defeated by the Persian army in 480 BCE.
After defeating the Greek navies at Artemesium, the Persian army moved to Athens and occupied it.
The Persian army, and the armies of the Greek city-states.
The Persian army, and the armies of the Greek city-states.