Agamemnon is only the first play of the great tragic trilogy, the Oresteia. Aeschylus wrote the Oresteia around 458 B.C.E.. It is his sole trilogy to survive intact. The two other plays, Choephori and Eumenides, and a lost satyr play called Proteus won its author first prize at the Great Dionysa that same year. A dramatic competition whose later victors included Sophocles and Euripides, the Great Dionysa took place once a year in Athens during the festival of Dionysus. The conventions of the competition were such that dramatists were responsible for nearly every aspect of production and staging, from composition of the plays themselves to costumes and scenery. In fact, Aeschylus probably acted in the first performances of the Oresteia. Plays were judged according to both high aesthetic criteria and the approval of the general audience. In his own time Aeschylus gained a reputation for dynamic and ornate sets, as well as for stunning sound and visual effects. He is considered by historians of Greek tragedy to be a major innovator in these areas.
The Oresteia spans two generations of the house of Atreus, while recounting, in different places, the line's unfortunate history, recent and remote. In Agamemnon, the king returns from Troy to Argos, where he is murdered by his wife; in Choephori, Agamemnon's son, Orestes, avenges his father by killing his mother and her lover, Aegisthus; and finally, in Eumenides, the bloodthirsty Harpies haunt Orestes until his final absolution by Athena's divine justice.
It is impossible to understand Aeschylus' grander theological and political project in the Oresteia by reading Agamemnon alone. Agamemnon stands on its own, but it is greatly enriched by the other two plays. One must read the others to see not only the scope and grandeur of this project, but its tightness of theme and symbolism, and its brilliant resolution. However, in Agamemnon we find the kernel of what is to come in Choephori and Eumenides. After all, Cassandra prophecies the key plot events through the end of Choephori, and the Chorus' refrain, "Sing sorrow, sorrow: but good win out in the end," anticipates the just resolution of the trilogy in the final play. But the play itself ends with a barrage of questions particularly centered around human guilt and divine causality. The vicious cycle of vengeance illustrated so poignantly in Agamemnon points to the inadequacy of humans, yet throughout the play gods remain strangely silent. How can this be? Their intervention is sure to come?that is all we know.
The tyranny under which Argos finds itself at the end of Agamemnon corresponds in a very broad way some events in the biographical career of Aeschylus. During his life, Aeschylus is know to have made at least two visits to the court of the Sicilian tyrant Hieron. It was a place that lured some of the other great poets of his day, Simonides, Pindar, and Bacchylides. He was also alive to see the democratization of Athens. The tension between, tyranny and democracy, is introduced in Agamemnon and, again, is developed more in the next two plays.