In addition to the Spartiates, several other Greek city-states sent troops to Thermopylae to defend against Xerxes' army. The city of Thespiae which was located in Boeotia, dispatched  a contingent of 700 warriors which comprised a significant portion of their army.  This band of warriors were led by Demophilus, the son of Diadromes. It was on the third and final day of the Battle of Thermopylae that the remnants of the Thespian contingent, while not the equivalent of the Spartans in training, armor, weaponry and tactics, fought and died alongside the remaining Spartiates to the bitter end. In the process, these valiant Greek warriors inflicted heavy casualties upon the Persian forces before succumbing to attrition.  For this action, the city of Thespiae received the same fate as the city of Athens by being burned to the ground by the invading Persian army. While the Thespian contribution to Thermopylae has not been totally overlooked, it has been minimized because of the overwhelming Spartan superiority as described above.

King Leonidas and the 300 Spartans have become synonymous with bravery and self-sacrifice, consequently, so should Demophilus and the 700 Thespians.  They were ordered by King Leonidas to withdraw along with the remaining Greek warriors before their position at Thermopylae was surrounded. However, the Thespians refused to leave and it was during the fighting of those final hours that Herodotus praised the Thespian warrior Dithyrambus, son of Harmatides, who it was noted, excelled in this decisive battle.