Darius was in the midst of his preparations for a third expedition to Greece, when all his plans were cut short by death. His son and successor, Xerxes I., now became King of Persia in his stead.
The new monarch was not inclined to renew the struggle with the Greeks; but his courtiers and the exiled Greeks who dwelt in his palace so persistently urged him to do it, that he finally consented. Orders were then sent throughout the kingdom to get ready for war, and Xerxes said that he would lead the army himself.
During eight years the constant drilling of troops, manufacture of arms, collecting of provisions, and construction of roads, were kept up all through Asia. A mighty fleet lay at anchor, and the king was almost ready to start. Rumors of these great preparations had, of course, come to the ears of the Greeks. All hearts were filled with trouble and fear; for the coming army was far larger than the one the Athenians had defeated at Marathon, and they could not expect to be so fortunate again.
When the Spartans saw the terror of the people, they regretted having angered the king by killing the Persian messengers, and wondered what they could do to disarm his wrath. Two young men, Bulis and Sperthias, then nobly resolved to offer their lives in exchange for those that had been taken.
They therefore set out for Persia, and, having obtained permission to enter the palace, appeared before the king. Here the courtiers bade them fall down before the monarch, and do homage to him, as they saw the others do. But the proud young men refused to do so, saying that such honor could be shown only to their gods, and that it was not the custom of their country to humble themselves thus. Xerxes, to the surprise of his courtiers did not at all resent their refusal to fall down before him, but kindly bade them make their errand known.