Atreus was murdered by Aegisthus, who took possession of the throne of Mycenae and ruled jointly with his father Thyestes. During this period Agamemnon and Menelaus took refuge with Tyndareus, king of Sparta, whose daughters Clytemnestra and Helen they respectively married. By Clytemnestra, Agamemnon had three daughters, Iphigeneia, Electra, Chrysothemis, and a son, Orestes.
Menelaus succeeded Tyndareus, and Agamemnon, with his brother's assistance, drove out Aegisthus and Thyestes, and recovered his father's kingdom. He extended his dominion by conquest and became the most powerful prince in Greece.
Agamemnon took part in the Trojan War on the side of the Greeks. Before Agamemnon's fleet left for Troy, however, the winds suddenly stopped and the ships would not move from Aulis. Agamemnon had offended the goddess Artemis by slaying a hind sacred to her, or any hind but in a sacred grove, and boasting himself a better hunter. The army was visited by a plague, and the fleet was prevented from sailing by the total absence of wind. Calchas announced that the wrath of the goddess could only be appeased by the sacrifice of Iphigeneia (daughter of Agamemnon). Agamemnon agreed and sacrificed her. Alternatively, Artemis accepted a deer in her place and took Iphigenia away to Crimea where she prepared others for sacrifice to Artemis. Still others sources claim he was prepared to but Artemis whisked her to Taurus in Crimea. Hesiod said she became the goddess Hecate.
Little is heard of Agamemnon until his quarrel with Achilles. Agamemnon took the maiden Briseis as his own and Achilles was angry--their anger forms one of the major plot points of the Iliad. After the capture of Troy, Cassandra, the daughter of Priam, fell to his lot in the distribution of the prizes of war.
On his return, after a stormy voyage, he landed in Argolis or was blown off course and landed in Aegisthus' country. Aegisthus, who in the interval had seduced Clytemnestra, invited him to a banquet at which he was treacherously slain, Cassandra also being put to death by Clytemnestra. According to the account given by Pindar and the tragedians, Agamemnon was slain by his wife alone in a bath, a piece of cloth or a net having first been thrown over him to prevent resistance. Her wrath at the sacrifice of Iphigenia, and her jealousy of Cassandra, are said to have been the motives of her crime. The murder of Agamemnon was avenged by his son Orestes.
Although not the equal of Achilles in bravery, Agamemnon is a dignified representative of kingly authority. As commander-in-chief, he summons the princes to the council and leads the army in battle. He takes the field himself, and performs many heroic deeds until he is wounded and forced to withdraw to his tent. His chief fault is his overweening haughtiness, due to an over-exalted opinion of his position, which leads him to insult Chryses and Achilles, thereby bringing great disaster upon the Greeks.
But his family had been marked out for misfortune from the outset. His kingly office had come to him from Pelops through the blood-stained hands of Atreus and Thyestes, and had brought with it a certain fatality which explained the hostile destiny which pursued him.
The fortunes of Agamemnon have formed the subject of numerous tragedies, ancient and modern, the most famous being the Oresteia of Aeschylus. In the legends of Peloponnesus, Agamemnon was regarded as the highest type of a powerful monarch, and in Sparta he was worshipped under the title of Zeus Agamemnon. His tomb was pointed out among the ruins of Mycenae and at Amyclae.
In works of art there is considerable resemblance between the representations of Zeus, king of the gods, and Agamemnon, king of men. He is generally characterized by the sceptre and diadem, the usual attributes of kings.