The chief protagonist of The Iliad is Achilles, the great Achaean warrior whose rage instigates the action of Homer’s story. At the very beginning of the poem, Achilles finds himself in conflict with the Achaean king, Agamemnon, who has decided to take for himself Achilles’s beloved war prize: the maiden Briseis. Agamemnon’s action deeply upsets Achilles, in part because it represents a personal betrayal but more crucially because it compromises Agamemnon’s reliability as a leader. Instead of winning glory in battle and earning a war prize for himself, Agamemnon simply abuses his power to take what he wants. Scandalized by Agamemnon’s failure to abide by the norms of warrior ethics, Achilles decides to remove himself from the fight in order to demonstrate, through his absence, the value he brings to the Achaean army. He also goes further, employing his mother, Thetis, to convince Zeus to favor the Trojans in war, thereby making Agamemnon suffer more deeply. For much of the poem, Achilles watches from the margins as the Trojans press in on the Achaeans. And whenever anyone tries to convince him to rejoin the fight, he roundly refuses. 

When Achilles finally relents, it is not because he’s had a fundamental change of heart. Like all of the characters in The Iliad, Achilles doesn’t undergo any significant character development over the course of the story. Achilles’s motivation remains grounded in revenge, but instead of continuing to seek revenge against Agamemnon, Achilles returns to battle in order to slay Patroclus’s killer, Hector. Achilles’s rage proves so intense that he fights the river god Scamander and racks up 24 kills in the course of just two books. Nor does his rage abate once he succeeds in killing Hector. Achilles straps Hector’s body to his chariot and drags the corpse around in an attempt to add insult to injury. Achilles’s rage only begins to wane when Hector’s father, King Priam of Troy, sneaks into Achilles’s tent and begs to take his son’s body home. When faced with Priam’s grief, Achilles relents. Not only does he release Hector’s body but he also promises Priam that the Achaean army will refrain from fighting until the Trojans can properly bury their dead hero. With the rage of Achilles finally abated, the poem comes to an end.