Xerxes, the "Great King" of the Persians - seen here on a relief originally located at Persepolis - was bent on subduing the Greeks. His father, Darius I, had embarked on a similar mission but was defeated at Marathon. Herodotus, in his Histories, tells us about the plans of the Great King (who also wanted to conquer all of Europe):
My intent is to throw a bridge over the Hellespont and march an army through Europe against Greece, that thereby I may obtain vengeance from the Athenians for the wrongs committed by them against the Persians and against my father. Your own eyes saw the preparations of Darius against these men; but death came upon him, and balked his hopes of revenge. In his behalf, therefore, and in behalf of all the Persians, I undertake the war, and pledge myself not to rest till I have taken and burnt Athens, which has dared, unprovoked, to injure me and my father.
Long since they came to Asia with Aristagoras of Miletus, who was one of our slaves, and, entering Sardis, burnt its temples and its sacred groves; again, more lately, when we made a landing upon their coast under Datis and Artaphernes, how roughly they handled us ye do not need to be told.
For these reasons, therefore, I am bent upon this war; and I see likewise therewith united no few advantages. Once let us subdue this people, and those neighbours of theirs who hold the land of Pelops the Phrygian, and we shall extend the Persian territory as far as God's heaven reaches. The sun will then shine on no land beyond our borders; for I will pass through Europe from one end to the other, and with your aid make of all the lands which it contains one country.
In 480 BC, Xerxes (who ruled from 486 to 465) was victorius at Thermopylae and Artemisium. He also sacked Athens but encountered a major setback at Salamis.
In this photograph, we see Xerxes on a relief honoring his father, Darius I (also known as "The Great"). The relief was originally located in Persepolis, on the north stairs of the audience hall (Apadana). It is now maintained in Tehran, at the National Archaeological Museum.