Xerxes played an extremely significant role in inspiring, preparing and mapping out the second Persian invasion of Greece. He also played an important role in deciding the outcome of the campaign. Any assessment of a Persian leader must be based largely on Greek sources. Some bias is therefore inevitable. It is consequently necessary to included only the less disputable evidence from relatively impartial sources to judge Xerxes contribution to the Persian Wars.
Xerxes influence on the 2nd Persian Wars can be categorized into three areas; What provoked him to begin the invasion, the preparation as well as the leadership throughout the campaign. It must also be deduced how these factors effected the wars outcome.
Xerxes decision to begin a campaign against Greece was provoked by a number of factors. These included his responsibility as king, revenge against Greece, power combined with the influences of others.
Xerxes responsibility as king encouraged him to expand the Persian Empire. According to Herodotus Persia's tradition of expansion had "never yet remained inactive". As the son of Darius he intended to follow in the footsteps of his father, to carry on his fathers work. Herodotus states that Xerxes duty was to "add as much power as they (his ancestors) did to the Persian Empire". Xerxes duty as king encouraged him to expand the Persian Empire and thus begin the 2nd Persian Wars.
Xerxes also had revenge as another motive for his invasion. Sources for this were numerous. Athens and Eretria burnt Persian temples during the Ionian revolt. His fathers defeat at Marathon would also have contributed. According to Herodotus the campaign was "to get satisfaction and revenge". Herodotus also recounts an alliance between Athens and Persia. Athens however repudiated the alliance in supporting the Ionian Revolt. The historian R. Grainger felt that the fundamental cause of military action was Athens "action as a contract breaker".