Because the Persian Army wanted to defeat the Greek city-states that supported the uprisings in Ionia, part of modern-day Turkey, against the Persian Empire.
The Greeks did
The battle of Marathon began in 490 BC. The battle took place between the Persian Empire and the Greeks. Eventually, the Greeks won the war.
The Greeks.
The Battle of Marathon was won by Athens and its ally Plataia in 490 BCE.
The Persians .
The Greeks
Greeks versus Persians .
defence
defence
Marathon, Greece .
In 490 BC Greeks victoriously fought Persians in the Battle of Marathon in an attempt from King Darius I to subjugate Greece.
Athens won at Marathon. Rome won against Carthage.