Cleomenes was a remarkable man. In fact, his spirit was too great for the small city-states of Greece. The fact that our sources say that he was insane tells a lot about how he was regarded by his contemporaries, who had never seen more of the world than their own town. In 488, king Cleomenes died under mysterious circumstances and was succeeded by his half-brother Leonidas, who strengthened his claim to the throne by marrying Cleomenes' daughter Gorgo. When the Persian king Xerxes invaded Greece in 480, Leonidas commanded the Greek advance guard at Thermopylae, and was killed in action (September 480).
He should have been succeeded by his younger brother Dorieus, but he was already dead, and therefore, the new king was Cleombrotus. His reign started terribly. The Persians broke through and occupied Athens. Cleombrotus decided to defend Greece at the Corinthian isthmus, where he ordered a wall to be build. At more or less the same time, the Greek fleet - informally commanded by the Athenian Themistocles - defeated the Persian navy at Salamis (29 September). Cleombrotus might have pursued the retreating Persian army, but the omens were bad (there was an eclipse on 2 October). He died a couple of days later, probably of natural causes.
Now, Pleistarchus, the son of Leonidas and Gorgo, should have become king, but he was too young, and therefore, Cleombrotus' son Pausanias was recognized as regent. He faced a difficult situation: the Persian army was still somewhere in northern Greece and its commander Mardonius had opened negotiations with the Athenians. If they would offer earth and water to the Persians (i.e., surrender), the invaders could use the Athenian navy and attack the Peloponnese everywhere they wanted.It seems that Pausanias and the other king, Leotychidas, wanted the best of both worlds: not fighting a war, and not aiding Athens. Our main source, the Histories by the Greek researcher Herodotus of Halicarnassus, clearly show that there were big diplomatic complications in the winter of 480/479. Eventually, the Athenians did not abandon the Greek cause, and Sparta decided to aid its ally. In the early summer of 479, when the Persian army of Mardonius had reoccupied Athens, Pausanias and an army set out for central Greece. It crossed the Cithaeron mountain range, and this forced Mardonius to retreat from Athens. The two armies were facing each other in Boeotia, north of a small town called Plataea. Herodotus offers a confused account of marching and counter-marching before the real battle was fought, somewhere in July. What seems certain is that the Persians were able to repel their opponents from the sources, that there were nightly maneuvers, that Mardonius was able to break through but was killed in action, and that the Greeks were able to attack the Persians when no one expected it. In the end, the Spartans defeated the Persian main force, and the Athenians captured the Persian camp (more).
Herodotus hardly mentions Pausanias' measures. It is possible that the battle of Plataea was indeed very much "a soldier's battle" and that the generals did not really play a large role; but its equally likely that Pausanias' leadership was belittled.
In the spring of 478, Pausanias led a Greek expeditionary force first to Cyprus and then to Byzantium. The Athenian leader Xanthippus, father of Pericles, had already captured Sestus near the Hellespont. If the Greeks would also take Byzantium, they would control the straits and could keep out the Persians. It was an important campaign, but Pausanias lost authority when rumors were spread that he wanted to collaborate with the satrap of nearby Hellespontine Phrygia, Artabazus. He was immediately recalled by the Spartan authorities, and the Athenian commander Aristides -who may have been behind the rumors- took over the command of the Greek army.
Meanwhile, Pausanias had returned to Sparta, where he was accused but found innocent. Yet, after this incident, Sparta decided to remain outside the Greek war against Persia. Athens, using its navy, continued the struggle, founded the Delian League, and started to build an empire.
Pausanias did not stay in Sparta. Giving up the regency, he returned to Byzantium, where he seems to have tried to found a small kingdom of his own. This was against the Athenian interests, and Cimon, son of Miltiades, expelled him. Now, Pausanias settled in Colophon (in Asia Minor), but in 471, he was again accused of Persian sympathies and forced to return to Sparta. Again, he was found innocent, and the accusation that he was conspiring with the helots was not substantiated either. Yet, it appears that he had tried to make some sort of arrangement for the helots; Spartan manpower was declining and it is likely that Pausanias tried to do something about it.
Nevertheless, he had many enemies and was forced to flee to the shrine of Artemis. No one dared to bring him food, and he died in the temple.
Pausanias had a son named Pleistoanax, who succeeded Pleistarchus as king in 459 and reigned for half a century.