Battle of Thermopylae army sizes 480BCE

2,500 years ago, in August or September 480BCE, the Battle of Thermopylae saw a vastly outnumbered Greek force hold out against one of the largest armies ever assembled; in what has been romantically remembered as the last stand of the 300 Spartans.

Background

Around the turn of the fifth century BCE, the Achaemenid Empire (or the First Persian Empire) was the world's largest and most powerful kingdom, stretching from present-day China to the Balkans and North Africa. In 492 BCE, King Darius launched the first Persian invasion of Greece, as a means of punishing the Greek cities, who had previously aided an Ionian Greek rebellion against Darius in Asia Minor. After two years of war, an alliance of Greek states finally defeated the Persians at the Battle of Marathon in 490BCE. Ten years later, Darius' successor, Xerxes, sought revenge and launched the second Persian invasion of Greece, amassing one of the largest armies the world had ever seen. Ancient sources claimed that the Persian army numbered between 2.5 and four million, however most modern estimates claim that it was a few hundred thousand at most. As the Persian army swept southwards, most Greek states surrendered, although a small number united and sent their armies to head off the Persians at the narrow pass of Thermopylae, while their navies created a blockade at the straits of Artemisium.

The build-up

Modern estimates claim that there were around 7,000 Greek soldiers sent to defend the narrow pass at Thermopylae, which was described as a 15 meter stretch between sheer cliffs and treacherous waters. This force was led by the Spartans and their king***, Leonidas; Sparta had the only professional army in Greece, however the battle coincided with a period of sacred religious and Olympic celebrations when fighting was not permitted, meaning Sparta sent just 300 veteran warriors to Thermopylae. Other states also sent relatively small numbers for similar reasons, as well as their reluctance to send their armies so far to the north. Despite these vastly inferior numbers, the Greek style of fighting was much better suited to the terrain at Thermopylae. Persian armies favored mobile battles, using archers to inflict most damage before sending in a combination of lightly armored soldiers and cavalry units to clean up remaining forces. The Greeks, however, used heavily armored hoplites in compact, phalanx formations, and preferred close-quarters combat.

Battle of Thermopylae

When the Persians reached Thermopylae, Xerxes waited four days before attacking, assuming that the Greeks would disperse at the sight of his army; when they did not, Xerxes ordered them to surrender their weapons, to which Leonidas famously replied "molon labe" or "come and take them". Xerxes then launched his attack, however, his archers inflicted little damage against the heavily armored Greeks and their heavy, bronze shields. Persian foot soldiers and cavalry, including the professional, heavily armored "Immortals", then suffered heavily at the hands of the Greek defenders. It was only after two days of fighting when the Persians gained the upper hand; a local shepherd, seeking reward, led a Persian force around a hidden path in the mountains, where they outflanked the Greeks. Surrounded, Leonidas ordered most of his forces to fall back, while the Spartans, Thebans, Thespians and helots remained. Eventually, King Leonidas and the rear guard were defeated as they protected their comrades' retreat (there are some reports of the Thebans surrendering). Despite losing the battle, the actions of the Greeks delayed the Persian advance into Greece, and bought their comrades enough time to regroup. The Greek armies and navies were then able to organize further defenses, and eventually defeat the invasion at the battles of Salamis and Plataea. By winning this war, the Greeks prevented the Persians from extending their empire and influence across Europe, in a war that likely altered the course of human history and development for all time.