When it was released in 1962, critics saw the movie as a commentary on the Cold War, referring to the independent Greek states as "the only stronghold of freedom remaining in the then known world", holding out against the Persian "slave empire".
Xerxes I of Persia leads a vast army of soldiers into Europe to defeat the small city-states of Greece, not only to fulfill the idea of "one world ruled by one master", but also to avenge the defeat of his father at the Battle of Marathon ten years before. Accompanying him are Artemisia, the Queen of Halicarnassus, who beguiles Xerxes with her feminine charm, and Demaratus, an exiled king of Sparta, to whose warnings Xerxes pays little heed.
In Corinth, Themistocles of Athens wins the support of the Greek allies and convinces both the delegates and the Spartan representative, Leonidas I, to grant Sparta leadership of their forces. Outside the hall, Leonidas and Themistocles agree to fortify the pass at Thermopylae until the rest of the army arrives. After this, Leonidas learns of the Persian advance and travels to Sparta to spread the news.
In Sparta, his fellow king Leotychidas is fighting a losing battle with the Ephors over the religious festival of Carnea that is due to take place, with members of the council arguing that the army should wait until after the festival is over before it marches, while Leotychidas fears that by that time the Persians may have conquered Greece. Leonidas decides to march north immediately with his personal bodyguard of 300 men, who are exempt from the decisions of the Ephors and the Gerousia. They are subsequently reinforced by Thespians led by Demophilus and other Greek allies.
After several days of fighting, Xerxes grows angry as his army is repeatedly routed by the Greeks, with the Spartans in the forefront. Leonidas receives word that, by decision of the Ephors, the remainder of the Spartan army, rather than joining him as he had expected, will only fortify the isthmus in the Peloponnese and will advance no further. The Greeks constantly beat back the Persians, and following the defeat of his personal bodyguard in battle against the Spartans, Xerxes begins to consider withdrawing to Sardis until he can equip a larger force at a later date. As he prepares to withdraw, however, Xerxes receives word from the treacherous and avaricious Ephialtes of a goat-track through the mountains that will enable his forces to attack the Greeks from the rear. Promising to reward Ephialtes for his betrayal, Xerxes sends his army onward.
Once Leonidas realizes he will be surrounded, he sends away the Greek allies to alert the cities to the south. Being too few to hold the pass, the Spartans instead attack the Persian front, where Xerxes is nearby. Leonidas is killed in the melée. Meanwhile, the Thespians, who had refused to leave, are overwhelmed (offscreen) while defending the rear. Surrounded, the surviving Spartans refuse Xerxes's demand to give up Leonidas' body. They are then annihilated by arrowfire.
After this, narration states that the Battle of Salamis and the Battle of Plataea end the Persian invasion, which could not have been organized without the time bought by the 300 Spartans who defied the tyranny of Xerxes at Thermopylae. One of the final images of the film is the memorial bearing the epigram of Simonides of Ceos, which is recited.
The battle scenes were shot near the village of Perachora, on the mainland side of the Corinth Canal, as it was impossible to shoot at the actual location in Thermopylae where 2,500 years of silt has shrunk the Malian Gulf drastically since the battle in 480 B.C., turning the strait where the battle was fought into a broad coastal plain. Some 5,000 members of the Hellenic Army were loaned by the Greek Ministry of National Defence to portray both the Spartans and the Persians.
Despite Cold War connotations the film was dubbed in Russian and it was shown in the USSR in 1970. The film was very popular there—27.1 million of viewers had seen it.Comic book -Dell Movie Classic: Lion of Sparta (January 1963)Novelisation - John Burke - The 300 Spartans Signet, New York; First Printing edition (1962)
Comic artist Frank Miller saw this movie as a boy and said "it changed the course of my creative life". His graphic novel 300 is about the Battle of Thermopylae, and in 2006, the book was adapted into a successful film.