The Iliad recounts a brief but crucial period of the Trojan War, a conflict between the city of Troy and its allies against a confederation of Greek cities, collectively known as the Achaeans. The conflict began when Paris, the son of Troy’s king Priam, seized a willing Helen, the most beautiful woman in the world, from the Achaean king Menelaus. The Achaeans raised a massive army and sailed to Troy, bent on winning Helen back by force.
As the story begins, the war is in its ninth year. The Achaeans have recently sacked a nearby city, taking several beautiful women captive along with a lot of treasure. Chryses, a priest of Apollo from the sacked city, approaches the Achaean camp and asks Agamemnon, the leader of the Achaeans, to release his daughter, who is one of the captives, from slavery. Agamemnon refuses. Chryses prays to Apollo to punish the Achaeans, and Apollo rains down a plague on the Achaean army.
The plague ravages the Achaean army. Desperate for an answer, the Achaeans ask the prophet Calchas about the plague’s cause. Calchas instructs Agamemnon to give back Chryses’ daughter. Agamemnon agrees reluctantly, but demands that he be given Briseis, the captive girl given to the warrior Achilles, as compensation. Achilles is enraged by Agamemnon’s demand and refuses to fight for Agamemnon any longer.
Achilles, the greatest of the Achaean fighters, desires revenge on Agamemnon. He calls to his mother Thetis, an immortal sea-nymph, and asks her to beseech Zeus to turn the tide of the war against the Achaeans. Since Achilles is fated to die a glorious death in battle, an Achaean collapse will help give Achilles glory, allowing him to come to their aid. Zeus assents to Thetis’ request.
On the battlefield, Paris and Menelaus agree to duel to end the war. Menelaus is victorious, but the Trojans break the agreement sworn to beforehand. The armies plunge into a battle that lasts several days. In the fighting, many soldiers distinguish themselves, including the Achaean Diomedes and Priam’s son Hector. The tide of battle turns several times, but the Trojan forces under Hector eventually push the Achaeans back to the fortifications they have built around their ships.
Meanwhile, a surrogate conflict is being waged between the gods on behalf of the Trojans and Achaeans. Athena, Hera, and Poseidon support the Achaean forces, while Apollo, Aphrodite, and Ares support the Trojans. As the battle rages on, the gods give strength and inspiration to their respective champions. Eventually Zeus, planning to shape the conflict by himself so that he may fulfill his promise to Thetis, bans intervention in the war by the other gods. Zeus helps engineer the Trojan advance against the Achaeans.
Under immense pressure, the elderly Achaean captain Nestor proposes that an embassy be sent to Achilles in order to convince him to return to battle. Achilles listens to their pleas but ultimately refuses, stating that he will not stir until the Trojans to attack his own ships. After a prolonged struggle, the Trojans finally break through the Achaean fortress, threatening to burn the ships and slaughter the Achaeans.
Achilles’ inseparable comrade Patroclus, fearing the destruction of the Achaean forces, asks Achilles if he can take his place in battle. Achilles eventually agrees, and as the first Achaean ship begins to burn, Patroclus leads out Achilles’ army, dressed in Achilles’ armor in order to frighten the Trojans. Patroclus fights excellently, and the Trojans are repulsed from the ships. However, Patroclus disobeys Achilles’ order to return after driving back the Trojans. He pursues the Trojans all the way to the gates of Troy. Zeus, planning this sequence of events all along, allows Apollo to knock Patroclus over. Hector then kills Patroclus as he lies on the ground, and a battle breaks out over Patroclus’ body. Hector strips Achilles’ armor from Patroclus, but Menelaus and others manage to save the body.
When Achilles learns of Patroclus’ death, he is stricken with grief. Desiring revenge on Hector and the Trojans, Achilles reconciles with Agamemnon. His mother Thetis visits the smith god Hephaestus, who forges new, superhuman armor for Achilles, along with a magnificent shield that depicts the entire world. Meanwhile, the Trojans camp outside their city’s walls, underestimating Achilles’ fury. The next day, Achilles dons his armor and launches into battle, slaughtering numerous Trojans on the plains of Troy. Achilles also fights the river god Xanthus, who becomes upset with Achilles for killing so many Trojans in his waters.
The Trojans flee from the rage of Achilles and hide inside the walls of Troy. Hector alone remains outside the wall, determined to stand fast against Achilles, but as Achilles approaches him, Hector loses his nerve and begins to run. Achilles chases Hector around the walls of Troy four times, but eventually Hector turns and faces Achilles. With the help of Athena, Achilles kills Hector. He attaches Hector’s corpse to his chariot and drags the body back to the Achaean camp as revenge for Patroclus’ death.
Achilles, still grieving, holds an elaborate funeral for Patroclus, which is followed by a series of commemorative athletic games. After the games, Achilles continues to drag Hector’s body around Patroclus’ corpse for nine days. The gods, wishing to see Hector buried properly, send Priam, escorted by Hermes, to ransom Hector’s body. Priam pleads with Achilles for mercy, asking Achilles to remember his own aging father. Achilles is moved by Priam’s entreaty and agrees to give back Hector’s body. Priam returns to Troy with Hector, and the Trojans grieve for their loss. A truce is declared while the Trojans bury Hector.