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.

This sense of predestination points to an important difference between ancient and modern fiction. Much of modern fiction creates a sense of dramatic tension by keeping the reader wondering how a story will end. Often a story’s ending depends upon the individual characters and the choices that they make according to their respective personalities. In contrast, ancient narratives often base themselves on mythological tradition, and ancient audiences would have listened to a given story already aware of its outcome. Tension in this scenario arises not from the question of how a character’s mind-set will affect the story’s events but rather from the question of how the story’s events will affect a character’s mindset. For example, the poem creates a sense of drama and poignancy in its portrayal of Hector, who continues to fight valiantly for Troy even though he knows in his heart—as he tells Andromache in Book 6—that he is doomed to die and Troy doomed to fall. Similarly, Achilles eventually rejoins the battle despite his knowledge that the glory of fighting will cost him his life. The drama comes not from waiting to see how the story ends but from waiting to see how the characters respond to an end already foreseen.

Some of the details of the Iliad’s plot do depend on individual characters’ choices, however. Achilles faces the dilemma of whether to enter the battle and save his comrades or stew in his angry self-pity and let them suffer. These inner struggles of an individual character create not only a sense of drama but often a sense of irony as well. In Book 1, Achilles asks Zeus, via Thetis, to punish the Achaeans for Agamemnon’s insolence in demanding the maiden Briseis. Now, as Zeus continues to oblige, helping the Trojans, Achilles loses his beloved comrade Patroclus. In another twist of irony, the death of Patroclus later motivates Achilles to rejoin the Achaean army and lead it against Troy, the very cause that he had forsworn before the beginning of the Iliad.

Some commentators detect a change in the characterization of Hector in this part of the epic. Earlier the undisputed champion of the Trojan army who criticizes Paris for retreating, Hector is twice shown fleeing battle after Patroclus’s entrance. The Trojan Glaucus shames him into returning the first time, and Hector’s uncle shames him into returning the second time (though Homer does point out that Zeus has made Hector cowardly). Additionally, Hector’s prediction that he will kill Achilles is empty boasting. Indeed, he can hardly even lay claim to having killed Patroclus, as both Apollo and another Trojan wound Patroclus before Hector can lay a hand on him.