It cost thousands of Greek lives.
The pass at Thermopylai was held to force a naval battle in which the Greek cities hoped to destroy the Persian navy. The sea battle failed, and the force defending the pass, having no further task, withdrew.
The Spartan contingent of 2,400 and the Thespian contingent of 1,400 continued to hold the pass, allowing 5,000 soldiers from other cities of the coalition to escape back to their cities before the Persian cavalry could break through and ride them down in open country.
It was a noble sacrifice.
The persion and some of the Greeks escape while groups among the Greeks continuing fighting and all of them died
They selflessly stayed to hold the pass until their allies could escape the field and gain sanctuary within the walls of friendly cities.
They did hold it for three days, to force a sea battle against the Persians. When the Persians won the sea battle, the Pass had no further use, and the Greek force was withdrawn. The Spartan and Thespian contingents stayed holding the pass to let the other city contingents escape.
Day 1 - the initial engagement at the pass, and naval skirmishing in the nearby strait of Artemesion. Day 2 - further fighting, and a naval battle at Artemesion. Day 3 - withdrawal of the other Greek land contingents and navy, and a last stand by the Spartan contingent to let the other land contingents escape.
It was a blocking action to bring on a navel action in the nearby strait in which the Greeks hopd to destroy the Persian naval threat. The naval battle failed so the Thermopylai pass was abandoned. The Spartan force of 2,400 (300 armoired infantry and 2,1oo light infantry) selflessly continued to hold the pass to let their 4,000 Greek allies escape, and died.
Their steadfastness in battle was complemented by their self-sacrifice at the end by remaining to hold the pass to allow their allies to escape destruction too.
The persion and some of the Greeks escape while groups among the Greeks continuing fighting and all of them died
Yes, the 300 Spartan hoplites with their 2,000 light infantry continued to hold the pass to let their 4,000 Greek allies escape and died to preserve them.
It was a small sideshow which had no historical impace. It did however become a symbol of self sacrifice, as the Spartan and Thespian contingents remained behind holding the pass and died to let the other Greek contingents escape.
They selflessly stayed to hold the pass until their allies could escape the field and gain sanctuary within the walls of friendly cities.
They did hold it for three days, to force a sea battle against the Persians. When the Persians won the sea battle, the Pass had no further use, and the Greek force was withdrawn. The Spartan and Thespian contingents stayed holding the pass to let the other city contingents escape.
The plan to hold the pass to provoke a sea battle in the nearby strait to destroy the Persian navy failed as the Greeks lost the sea battle. As this failed, the Greek holding force dispersed back to their cities. Leonidas and his Spartan 2,400 heavy and light infantry continued to hold the pass to let them escape. They were slaughtered.
The Spartans led a frce to hold the pass to force a sea battle in the nearby strait. When the Greeks lost the sea battle, the reason to hold the pass no longer existed. The Spartans selflessly kept holding the pass to let their allies escape, and were overwhelmed.
It was a holding operation to stop the Persian land advance into southern Greece. The object was to force the Persians to break the impasse with a flanking movement by sea, and the Greek naval forces were waiting, hoping to win a decisive sea battle in the nearby strait of Artemesion. The Greeks lost the sea battle and the force at Thermopylai, having fulfilled its function, was withdrawn. The Spartan and Thespian contingents remained behind to cover this withdrawal, sacrificing themselves to let the others escape. The Greek fleet reassembled in the strait at Salamis near Athens and there won the naval victory they had been seeking.
It was a holding operation to stop the Persian land advance into southern Greece. The object was to force the Persians to break the impasse with a flanking movement by sea, and the Greek naval forces were waiting, hoping to win a decisive sea battle in the nearby strait of Artemesion. The Greeks lost the sea battle and the force at Thermopylai, having fulfilled its function, was withdrawn. The Spartan and Thespian contingents remained behind to cover this withdrawal, sacrificing themselves to let the others escape. The Greek fleet reassembled in the strait at Salamis near Athens and there won the naval victory they had been seeking.
The Greeks allowed the center to give way thus exposing the Persian flanks to a concerted Greek assault causing the collapse of Persian forces who then sought to escape by sea - the Greeks then slaughtered the Persian forces attempting to escape . Look to the related link below which has an excellent representation of what occurred at the seminal battle of Marathon .
A valiant stand by the central Greek cities, and the sacrifice of the Spartans who fought to the death in order to allow their allies escape the field.