In 490 BCE the battle of marathon had begun. Darius did not lead the invasion of Greece in person but put his general Datis in charge of his army. The Greeks were lead by either Miltiades or Callimachus.
The assault tactics of the Persians were to come up against the Greeks with their large shields and spears. Also the Greek's organization of a line where each man's shield protected two.
When the persians rapidly fired arrows at the greek, they were ineffective against the bronze armored warriors.
At close quarters the greeks thinned enemy numbers with spears and swords , enveloping them until there were 6,150 Persian deaths and about 160 Greek deaths.
The few Persians who survived the Greeks, fled to their ships to sail back to Persia for more men for them to invade Athens with.
The Greeks heard word of this and sent a messenger to run 26 miles to Athens in order to warn he city about the attack from the coming Persians. The messenger reached the city an alerted them just in time before he died of exhaustion.