Thyestes killed Atreus. While Thyestes ruled Mycenae, the sons of Atreus, Agamemnon and Menelaus, were exiled to Sparta. There, King Tyndareus accepted them as the royalty that they were. Shortly after, he helped the brothers return to Mycenae to overthrow Thyestes, forcing him to live in Cytheria, where he died. As a token of good will and allegiance, King Tyndareus offered his daughters to Agamemnon and Menelaus as wives, Clytemnestra and Helen respectively. When Agamemnon left Mycenae for the Trojan War, Aegisthus seduced Agamemnon's wife, Clytemnestra, and the couple plotted to kill her husband upon his return. They succeeded, killing Agamemnon
History of Sparta head. It also seems to have changed the nature of the Peloponnesian League. From that time, major decisions were discussed. Sparta was still in charge, but it now had to rally its allies in support of its decisions. After hearing a plea for help from Athens who were facing the Persians at Marathon in 490 BC, Sparta decided to honor its laws and wait until the moon was full to send an army. As a result, Sparta's army arrived at Marathon after the battle had been won by the Athenians. In the second campaign, conducted ten years later by Xerxes,