Agamemnon was the king of Mycenae. He was the commander of the Greek army during the Trojan War.
Agamemnon gathered the reluctant Greek forces to sail for Troy. During the journey he angered Artemis for slaying an animal. A terrible wind blew upon the men, and the prophet Calchas announced that the wrath of the goddess could only be appeased by the sacrifice of Agamemnon's daughter Iphigenia. Agamemnon and his men reluctantly sacrificed her by luring her into a wedding, and her death satisfied Artemis, allowing the Greek army to advance towards Troy.
The Iliad narrates the conflict between Agamemnon and Achilles in the final moments of the war. Agamemnon captured Chryseis, and after he is forced to return her he takes Briseis, Achilles's daughter. Achilles quit the war after his mother convinces him to. Because Achilles was the greatest hero on the Greek side, the Greek army struggled immensely.