In the version as written by Frank Miller, the envoys sent by Xerxes of Persia have approached King Leonidas for the submission of the city-state of Sparta. The events that follow result in the Spartans dispatched to Thermopylae so that they will fight for their freedom and not live under the tyrannical Persian oppressor.War has been declared!
However, this happened ten years earlier, prior to the Battle of Marathon, when the Spartans were asked by the heralds to provide 'earth and water'. The Spartans' reply, 'You can find all the earth and water that you need at the bottom of the well.' This scene is probably the most famous from the movie, followed by the exhortation by King Leonidas 'This is Sparta!!!'