Most people know about the Battle of Thermopylae, even if they don't recognize the name. During the second Persian invasion of Greece, 300 Spartans fought against Xerxes I's forces on a narrow mountain pass. With such cinematic details, no wonder this sensational battle inspired the blockbuster film 300. However, both the film and popular imagination miss many important details about this battle. This concise history sheds light on the thousands of Greek citizen-soldiers who fought alongside the Spartans, forever changing the course of Greek identity and nationhood.