Agamemnon (pronounced a-ga-mem'-non), was the leading king of the Greek forces in the Trojan War. He became king of Mycenae by driving out his uncle, Thyestes, with the help of King Tyndareus of Sparta. Agamemnon was a son of Atreus, the husband of Clytemnestra (a daughter of Tyndareus), and the brother of Menelaus, who was the husband of Helen of Troy (Clytemnestra's sister).
Agamemnon and the Greek Expedition
When Helen was abducted by the Trojan prince Paris, Agamemnon led the Greek expedition to Troy to take back his brother's wife. In order for the Greek fleet to set sail from Aulis, Agamemnon sacrificed his daughter Iphigenia to the goddess Artemis.
Clytemnestra Seeks Revenge
When Agamemnon returned from Troy, he wasn't alone. He brought with him another woman as a concubine, the prophetess Cassandra, who was famous for not having her prophecies believed. This was at least a third strike for Agamemnon as far as Clytemnestra was concerned. His first strike had been killing Clytemnestra's first husband, the grandson of Tantalus, in order to marry her. His second strike was killing their daughter Iphigenia, and his third strike was flagrant disregard shown for Clytemnestra by parading another woman in her home. No matter that Clytemnestra had another man. Clytemnestra and her lover (Agamemnon's cousin), killed Agamemnon. Agamemnon's son Orestes took revenge by killing Clytemnestra, his mother. The Furies (or Erinyes) took vengeance on Orestes, but in the end, Orestes was vindicated because Athena judged that killing his mother was less heinous than killing his father.