Zeus wakes and sees the havoc that Hera and Poseidon have wreaked while he dozed in his enchanted sleep. Hera tries to blame Poseidon, but Zeus comforts her by making clear that he has no personal interest in a Trojan victory over the Achaeans. He tells her that he will again come to their aid, but that Troy is still fated to fall and that Hector will die after he kills Patroclus. He then asks Hera to summon Iris and Apollo. Iris goes to order Poseidon to leave the battlefield, which Poseidon reluctantly agrees to do, while Apollo seeks out Hector and fills him and his comrades with fresh strength. Hector leads a charge against the Achaeans, and while their leaders initially hold their ground, they retreat in terror when Apollo himself enters the battle. Apollo covers over the trench in front of the Greek fortifications, allowing the Trojans to beat down the ramparts once again.
The armies fight all the way to the ships and very nearly into the Greek camp. At the base of the ships, furious hand-to-hand fighting breaks out. Great Ajax and Hector again tangle. The archer Teucer fells several Trojans, but Zeus snaps his bowstring when he takes aim at Hector. Ajax encourages his troops from the decks of the ships, but Hector rallies the Trojans, and inch by inch the Trojans advance until Hector is close enough to touch a ship.
Meanwhile, Patroclus goes to Achilles’ tent and begs to be allowed to wear Achilles’ armor if Achilles still refuses to rejoin the battle himself. Achilles declines to fight but agrees to the exchange of armor, with the understanding that Patroclus will fight only long enough to save the ships. As Patroclus arms himself, the first ship goes up in flames. Achilles sends his Myrmidon soldiers, who have not been fighting during their commander’s absence, out to accompany Patroclus. He then prays to Zeus that Patroclus may return with both himself and the ships unharmed. The poet reveals, however, that Zeus will grant only one of these prayers.
With the appearance of Patroclus in Achilles’ armor the battle quickly turns, and the Trojans retreat from the Achaean ships. At first, the line holds together, but when Hector retreats, the rest of the Trojans become trapped in the trenches. Patroclus now slaughters every Trojan he encounters. Zeus considers saving his son Sarpedon, but Hera persuades him that the other gods would either look down upon him for it or try to save their own mortal offspring in turn. Zeus resigns himself to Sarpedon’s mortality. Patroclus soon spears Sarpedon, and both sides fight over his armor. Hector returns briefly to the front in an attempt to retrieve the armor.
Zeus decides to kill Patroclus for slaying Sarpedon, but first he lets him rout the Trojans. Zeus then imbues Hector with a temporary cowardice, and Hector leads the retreat. Patroclus, disobeying Achilles, pursues the Trojans all the way to the gates of Troy. Homer explains that the city might have fallen at this moment had Apollo not intervened and driven Patroclus back from the gates. Apollo persuades Hector to charge Patroclus, but Patroclus kills Cebriones, the driver of Hector’s chariot. Trojans and Achaeans fight for Cebriones’ armor. Amid the chaos, Apollo sneaks up behind Patroclus and wounds him, and Hector easily finishes him off. Hector taunts the fallen man, but with his dying words Patroclus foretells Hector’s own death.
Book 15 marks the beginning of the end for Hector and the Trojans, who have reached the height of their power and now face a downhill slope. From this vantage point, the end is in sight, and, correspondingly, Zeus now outlines the rest of The Iliad and beyond, predicting even the eventual fall of Troy, which occurs after the end of the poem. Zeus’s speech makes it clear to the reader that a predestined conclusion awaits the Achaeans and Trojans; he is thus able to summarize the story even before the events occur.