The Battle of Thermopylae, which inspired the movie, took place in 480 BC. The Persian Empire, led by king Xerxes, had already conquered much of Greece and was marching towards Athens. However, the Greeks managed to unite under the leadership of the Spartan king Leonidas, who was determined to defend his homeland.
Leonidas led a force of around 7,000 Greek soldiers, including the famous 300 Spartans, to the narrow pass of Thermopylae, where they planned to hold off the Persian army. The pass was chosen because it offered a strategic advantage to the Greeks, who could use their superior fighting skills to hold the Persians at bay.
The Persians, however, vastly outnumbered the Greeks, with estimates ranging from 70,000 to 250,000 soldiers. Despite these odds, Leonidas and his men fought valiantly for three days, inflicting heavy casualties on the Persians and holding their ground.
On the final day, however, a local traitor named Ephialtes revealed a hidden mountain path to the Persians, which allowed them to flank the Greek position. Realizing that defeat was inevitable, Leonidas dismissed the majority of his troops and committed his remaining force, the 300 Spartans, to a suicidal last stand.
The Spartans fought bravely, even after their weapons were broken, and managed to take down many Persian soldiers before eventually being overwhelmed. Leonidas himself was killed, but his sacrifice inspired the remaining Greeks to rally and eventually defeat the Persians in the Battle of Salamis.
The Battle of Thermopylae has become a symbol of Greek resistance and heroism, and the story of Leonidas and his 300 Spartans has inspired countless works of art, literature, and film.