He made one unsuccessful attempt to set up a colony in Africa and, when this failed, sought his fortune in Sicily, where after initial successes he was killed.

[5] Leonidas' relationship with his bitterly antagonistic elder brothers is unknown, but he married Cleomenes' daughter, Gorgo, sometime before coming to the throne in 490 BC.

[6] Leonidas was heir to the Agiad throne (successor of Cleomenes I) and a full citizen (homoios) at the time of the Battle of Sepeia against Argos (c. 494 BC).

His elder half-brother, king Cleomenes, had already been deposed on grounds of purported insanity, and had fled into exile when Athens sought assistance against the First Persian invasion of Greece, that ended at Marathon (490 BC).

'"[8] The product of the agoge, Leonidas was unlikely to have been referring to his royal blood alone but rather suggesting that, like his brother Dorieus, he had proved himself superior in the competitive environment of Spartan training and society, thus making him qualified to rule.

[9] Upon receiving a request from the confederated Greek forces to aid in defending Greece against the Persian invasion, Sparta consulted the Oracle at Delphi.

The Oracle is said to have made the following prophecy in hexameter verse: For you, inhabitants of wide-wayed Sparta, Either your great and glorious city must be wasted by Persian men, Or if not that, then the bound of Lacedaemon must mourn a dead king, from Heracles' line.

"[12] Many modern commentators are dissatisfied with this explanation and point to the fact that the Olympic Games were in progress or impute internal dissent and intrigue.

Whatever the reason Sparta's own contribution was just 300 Spartiates (accompanied by their attendants and probably perioikoi auxiliaries), the total force assembled for the defence of the pass of Thermopylae came to something between four and seven thousand Greeks.

The Persian elite unit known to the Greeks as "the Immortals" was held back, and two of Xerxes' brothers (Abrocomes and Hyperanthes) died in battle.

The King would have thought it wise to preserve those Greek troops for future battles against the Persians, but he knew that the Spartans could never abandon their post on the battlefield.

Herodotus believed that Leonidas gave the order because he perceived the allies to be disheartened and unwilling to encounter the danger to which his own mind was made up.

[20] A sign, under the statue, reads simply: "ΜΟΛΩΝ ΛΑΒΕ" ("Come and take them"), which was Leonidas' laconic reply when Xerxes offered to spare the lives of the Spartans if they gave up their arms.

[24] He is a central figure in Steven Pressfield's novel Gates of Fire,[25] and appears as the protagonist of Frank Miller's 1998 comic book series 300.