Darius was very busy preparing this other army to march against Greece. While the men were being drilled, he sent two messengers to the Greek towns and islands, bidding them surrender and give him earth and water.
By demanding “earth and water,” Darius meant that he wanted them to recognize him as their king, and as master of all their lands and vessels. The inhabitants of many of the islands and towns were so frightened by the messages sent by The Great King, that they humbly yielded; but when the messengers came to Sparta and Athens, they met with a different reception.
In both cities the people proudly replied that they were their own masters, and would not yield to the demands of the Persian king. Then, angered by the insolent command to give earth and water, the Spartans entirely forgot that the life of an ambassador is sacred. In their rage, they seized the Persians, flung one into a pit and the other into a well, and told them to take all the earth and water they wanted.
This conduct made Darius all the more angry, and he hastened his preparations as much as he could. He was so active that in a short time he was able to start out again, with an army of a hundred and twenty thousand men.
The generals of this force were Datis and Artaphernes, who were guided and advised by the traitor Hippias. The fleet was to land the army on the plain of Marathon, close by the sea, and only one day’s journey from Athens.
When the Athenians heard that the Persians were coming, they immediately decided to ask the Spartans, who were now their allies, to come to their aid, and help them drive back the enemy. As there was no time to lose, they chose as their messenger a fleetfooted Athenian, who made the journey of a hundred and fifty miles in a few hours, running every step of the way, and only seldom pausing to rest.