Four Persian Warriors, Palace of Darius I the Great, Suse. C. 500 BC. Glazed brick frieze in one of the capitals of the Achaemenid Empire, depicting four warriors at the sides of a column of cuneiform text in which the name of Darius can be recognized… [1920×1080] [OC]

…The frieze was probably inspired by the brick friezes of Babylon, although the technique is different. That may be a legacy from the Middle Elamite Period, which saw the appearance of decoration in glazed siliceous brick.

The warriors in the frieze are believed to be The Immortals, also known as the Persian Immortals. This name given by Herodotus to an elite heavily-armed infantry queued unit of 10,000 soldiers in the army of the Achaemenid Empire. This force also conformed the Imperial Guard. Herodotus describes the ‘Immortals’ as a heavy infantry professional corps constantly kept at a strength of exactly 10,000 men. The unit’s name came from the practice of immediately replacing any disabled man, maintaining the corps as a cohesive entity with that constant strength of 10,000. The practical result was this army could not be killed, thus the Immortals. These would be the Immortals the 300 faced at the battle of Thermopylae in the movie.

As usual, my apologies for inaccuracies and mistakes.