The Ancient Greeks have long been considered the forefathers of modern Western civilization, but the Golden Age of Athens and the spread of Greek influence across much of the known world only occurred due to one of the most crucial battles of antiquity: the Battle of Marathon. In 491 BC, following a successful invasion of Thrace over the Hellespont, the Persian emperor Darius sent envoys to the main Greek city-states, including Sparta and Athens, demanding tokens of earth and water as symbols of submission, but Darius didn't exactly get the reply he sought. According to Herodotus in his famous Histories, "Xerxes however had not sent to Athens or to Sparta heralds to demand the gift of earth, and for this reason, namely because at the former time when Dareios had sent for this very purpose, the one people threw the men who made the demand into the pit and the others into a well, and bade them take from thence earth and water and bear them to the king."

Thus, in 490 BC, after the revolt in Ionia had been crushed, Darius sent his general Mardonius, at the head of a massive fleet and invading force, to destroy the meddlesome Greeks, starting with Athens. The Persian army, numbering anywhere between 30,000 and 300,000 men, landed on the plain at Marathon, a few dozen miles from Athens, where an Athenian army of 10,000 hoplite heavy infantry supported by 1,000 Plataeans prepared to contest their passage. The Athenians appealed to the Spartans for help, but the Spartans dithered; according to the Laws of Lycurgus, they were forbidden to march until the waxing moon was full. Accordingly, their army arrived too late. Thus, it fell upon the Athenians to shoulder the burden. With their army led by the great generals Miltiades and Themistocles, the Athenians charged the outnumbering Persians. Outmatched by the might of the heavy, bronze-armored Greek phalanx, the inferior Persian infantry was enveloped and destroyed, causing them to flee for their ships in panic. The Athenians had won a colossal victory against an overwhelming and seemingly invincible enemy.

Somewhat ironically, the Battle of Marathon has been best commemorated by the race that bears its name, a tradition that started based on a legend that a Greek man named Pheidippides ran the 26.2 miles back to Athens in order to announce the Greek victory and subsequently collapsed and died as soon as he had done so. However, the importance of the battle itself cannot be overstated. The Battle of Marathon proved to be one of the biggest sources of enmity between the Greeks and Persians, and Darius' son Xerxes would seek to undo the results with his own invasion just years later. As it was, the rivalry between the Greeks and Persians would last for over 150 years and culminated with Alexander the Great's destruction of the Achaemenid Persian capital city of Persepolis. Marathon also positioned the city-state of Athens as a major power not only in Greece but throughout the Mediterranean and Near East, as their military, diplomatic, and economic influence grew after the battle.