Why does the Battle of Thermopylae in 480 BC still matter even though it was a defeat?

Thermopylae in 480 BC was a tactical loss but a strategic and moral victory, because the stand bought Greece time and proof that Persia could be resisted, setting up the later Greek wins at Salamis and Plataea.

Why did the Greeks choose to fight at a narrow pass at Thermopylae?

At Thermopylae in 480 BC the Greeks held the narrow coastal defile so Persia's huge numbers could not be brought to bear, since a Persian could only meet a Greek one or two at a time against the heavily armored hoplites fighting shoulder to shoulder in the phalanx.

How were the Greeks finally defeated at Thermopylae?

At Thermopylae in 480 BC the Greeks were betrayed rather than beaten, when a local named Ephialtes showed the Persians the Anopaia mountain path that came out behind the Greek position and let them be surrounded.

Were there really only 300 Spartans at Thermopylae?

No; at Thermopylae in 480 BC roughly 7,000 Greeks gathered under Leonidas I, including his 300 Spartiates plus Thespians, Thebans, Arcadians, Corinthians and others, though the 300 Spartans are the most remembered.

How large was the Persian army at Thermopylae in 480 BC?

Ancient writers claimed millions at Thermopylae in 480 BC, but modern estimates place the army of Xerxes I somewhere between 70,000 and 300,000, still overwhelming against the roughly 7,000 Greeks.

Who won the Battle of Thermopylae?

Persia under Xerxes I won the Battle of Thermopylae in 480 BC, overcoming the roughly 7,000 Greeks under Leonidas I after a local showed the Persians a mountain path that let them surround and destroy the defenders.

The Battle of Thermopylae, 480 BC: the 300 and the Hot Gates

In the late summer of 480 BC, a small Greek force chose a stretch of coast barely wide enough for a cart and dared the largest army the ancient world had ever assembled to come through it. For three days it could not. Thermopylae is remembered for the way it ended, but the reason it still matters is how nearly it worked.

Why a narrow pass

King Xerxes I of Persia had crossed into Greece to finish what his father Darius had begun a decade earlier at Marathon. His army was vast, ancient writers claim millions; modern estimates land somewhere between 70,000 and 300,000, still overwhelming. Numbers like that are only an advantage where they can be brought to bear. The Greek plan, urged by the Spartans, was to deny them the space: hold the coastal defile at Thermopylae, the "Hot Gates," named for its sulphur springs, where the mountains pinch the road against the sea.

Roughly 7,000 Greeks gathered there under the Spartan king Leonidas I: his own 300 Spartiates, plus Thespians, Thebans, Arcadians, Corinthians and others. In the bottleneck, a Persian could only ever meet a Greek one or two at a time, and the heavily armoured hoplite, fighting shoulder to shoulder in the phalanx with his long spear, was built for exactly that.

In the narrows, a hundred thousand men count for no more than the few who can reach the spears.

Three days at the wall

For two days the Persians threw wave after wave into the pass and were cut down against the old Phocian wall the Greeks had rebuilt. Even Xerxes' elite Immortals, his ten thousand household guard, could make no headway. The Greeks rotated fresh men to the front and, by some accounts, feigned retreats to draw the Persians onto their spears. The battle was going, impossibly, in the defenders' favour.

The path over the mountain

It was betrayed, not beaten. A local named Ephialtes, hoping for reward, showed the Persians the Anopaia path, a track through the hills that came out behind the Greek position. Warned he was about to be surrounded, Leonidas dismissed most of the allied contingents to fight another day and stayed to cover their retreat with his 300 Spartans, the 700 Thespians who refused to leave, and the Thebans. They were enveloped and killed to the last man; Leonidas fell with them, and the Persians fought bitterly over his body.

A defeat that won a war

Thermopylae was a tactical loss. Its value was strategic and moral. The stand, fought alongside the naval action at Artemisium the same days, bought Greece time and proof that Persia could be resisted. Within months the Greek fleet destroyed Xerxes' navy at Salamis, and in 479 BC the army was broken at Plataea. The invasion failed. A stone at the pass carried the epitaph for the fallen: they lay there still, obedient to their laws.