More than 300 in the pass
The 2006 film 300 puts one number at the centre, and that number is a real one. In 480 BCE Leonidas and the Spartans did stand in the pass at Thermopylae against the army of Xerxes I. Britannica's account of the battle puts a Greek army of about 7,000 there for the fight as a whole. The 300 were his bodyguard, not the whole Greek force.
Xerxes was finishing a quarrel his father had started. Darius I sent heralds in 491 BCE. The Athenians threw the heralds into a pit, and the Spartans threw theirs into a well. When Xerxes came, he skipped Athens and Sparta. A Spartan reply to a Persian order to lay down arms is remembered as "Come and take them," Molon labe.
Britannica gives the Persian host as somewhere between 70,000 and 300,000. The Greeks held for two days. Then Ephialtes betrayed a path around the pass. After a council, the main Greek army retreated. Leonidas stayed with his 300 bodyguards, some helots, and 1,100 Boeotians. Many, if not all, of that last group were killed, and the ancient sources differ on the details. A stone lion was set up soon afterward.
Britannica's narrative runs the fighting across three days in all: two days before the betrayal, then the smaller stand. The Persian range it prints is 70,000 to 300,000. Livius counts a garrison of 4,000 and a last stand of 300 Spartiates, 900 helpers, 700 Thespians, and 400 Thebans, and says Xerxes waited four days, while Britannica puts about 7,000 in the pass and keeps the last stand at the 300, some helots, and 1,100 Boeotians. The account to retell is that larger pass, and then the smaller mixed stand.
Livius still adds colour the battle page leaves open. It names the Immortals under Hydarnes on the Persian side. It calls the tale of Ephialtes hardly credible. It also says Herodotus seems confused about whether the Greeks left or were ordered away, and it points to a clash between his chapters 7.219 and 7.220. Charles Hignett called the reason Leonidas stayed an unsolved riddle. The oracle story, on that reading, was introduced as personal opinion and smells of propaganda.
The men who stayed were not only Spartans, even in the starker telling. Thebans later collaborated with Persia, and Livius notes that Plutarch accused Herodotus of malice on that point. An epitaph for the Spartan dead is given there as "Stranger, go tell the Spartans that here we are buried, obedient to their orders." Livius also floats possible full-moon nights of 17, 18, and 19 September, a dating the Britannica battle page does not fix.
The 300 remain in every careful account. Britannica calls them Leonidas's bodyguard. Livius calls them 300 Spartiates and then adds helpers, Thespians, and Thebans. The famous number is real. It is the king's guard, inside a larger stand. In 1955 King Paul of Greece unveiled a statue of Leonidas at the site.
What the pages share is the part worth keeping. The pass was not held, from the first hour, by 300 men alone. Allies were in the line, and a smaller mixed force remained when the larger army pulled back. Tomorrow's question is about a Roman building and the formal name beside its nickname.