In September of the year 490, the Persian forces landed at the sandy harbour of Marathon with an invasion force of 600 ships, 20,000 or more foot soldiers, and 800 cavalry. Also with them was the deposed tyrant of Athens, Hippias.
The Athenians immediately dispatched Phidippides to run to Spartan and seek their aid. But when he arrived there Phidippides found them in the middle of a religious festival. They would not send help until the festival had finished.
The Athenian hoplites would have to face the massed ranks of the Persians alone.
Outnumbered by 2:1, the Athenians at first took fright at their vast enemy, with its multicoloured costumes, turbans, and unfamiliar armour. However, after a heated debate amongst the Athenian generals, they opted to engage the enemy, advancing toward them at a run under a hail of arrows. But after a long and protracted struggle the Greeks emerged victorious. Aided by superior tactics, better equipment, and sheer determination they had achieved the impossible.
Over six thousand Persians lay dead. In contrast only 192 hoplites had perished on the Athenian side.
Background to the Greek colonies of Turkey
Phidippides' & the First Marathon
The Tactics Used At Marathon