In 480, the Persian king Xerxes invaded Greece, defeated his enemies at Artemisium and Thermopylae, and sacked Athens. Although his navy was severely damaged in the naval battle ofSalamis, it was obvious that the Persians were the strongest. So, the great king recalled many troops. This gave the Greeks the breathing space they needed, and they defeated Xerxes' right-hand man Mardonius at Plataea. More or less at the same time, a Greek expeditionary force attacked the remains of the Persian navy atMycale, and started to liberate the Greek towns in Asia Minor.
In 478, the Spartan prince Pausanias led a Greek expeditionary force to Byzantium. If he would take the city, the Greeks would control the Bosphorus and could keep the Persians out of Europe. However, Pausanias lost authority when rumors were spread that he wanted to collaborate with the satrap of nearby Hellespontine Phrygia, Artabazus. He was recalled by the Spartan authorities, and the Athenian Aristides, who may have been behind the rumors, took over the command of the Greek army.
Although Pausanias was cleared of all accusations, the Spartans now decided to remain outside the war against Persia. For Sparta, the main war aims had been reached now that a cordon sanitaire had been created in Asia Minor. If the Persians wanted to return to Europe, they first had to occupy the towns of the liberated Ionian Greeks. The Athenians had a different perspective. They felt related to the Ionians, and in their view, security could only be reached when their compatriots were safe as well. Therefore, they continued the struggle and founded the Delian League.
From the very first beginning, there appears to have been an element of rivalry with Sparta, as is suggested by the author of the Constitution of the Athenians, a little treatise that is (probably incorrectly) attributed to Aristotle of Stagira:
Aristides saw that the Spartans had gained a bad reputation because of Pausanias and urged the Ionians to break