On the Plot
The plot of the book and the film has a very big difference especially on its coverage and focus. The coverage of the film starts all the way from why the Trojan-Greeks conflict started up to the death of Achilles and the fall of Troy. While on the other hand, the book' onset is narrowed down to the ninth year of the Trojan war wherein the conflict between Achilles and Agamemnon is intensified. Aside from this the book ends the epic in the change of Achilles character. From the difference of the said coverage, it can be derived that the focus of the book is on the wrath of Achilles being resolved, while the film is the settlement of the conflict of the Trojans and Greeks. Even if the film's focus is on a more general conflict, our hero Achilles is not totally thrown off the periphery. He still is a very important character in the story. The direction of the war became dependent on his participation. The film is also very compressed and comprehensive. And to fit everything into place, some twists on the characters was made (which will be discussed in On the Characters). An example would be Briseis who was used to display the conflict between Achilles and Agamemnon. She is also used to put into story why he change his character in the near ending, like forgetting about the glory of war, letting the Myrmidons save themselves and sail home, and most important is the plotting of his death.
Other differences could be accounted on the change of audience. The audience of Iliad (Homer's audience, the Acheans, etc.) and modern audience of the film is culturally miles apart. Some of the results are changes of setting, cutting off too many repeated wars, less mythological appearances (will be discussed on The Themes), shortening of the characters profiling. The films setting is limited by of course production budget, the Trojan land (beach, walls of troy, battlefield in front of city walls) lost the books' rivers, mountainside, Mt Olympus settings, etc. The wars that took place in the film was also limited to battles that inflicts significant turn of the plot like, the encounter that yields the Greeks Briseis, the battle without Myrmidons, the battle that slew Patroclus and that which caused the fall of Troy. Again, one of the reason is budget and aside from that is audience. Modern audience will be bored with scenes that are insignificant to the general outcome. Lastly, the long character profiling would probably bore the audience but in Homer's case it will just stir his audiences' emotion once their place is mentioned, bringing up their honorable heritage.
On the Characters
One of the most significant change in character happened to Briseis. From a plain priestess from Khryse, she was converted as Hector's cousin. Changes made to her was strategic to make the film comprehensive of all significant events. We know that the wrath of Achilles is unleashed after the “Briseis incident”, this incident is used by the book and film very differently. The book used the taking away of Briseis as a symbol that Achilles' share of a victory from war is being robbed from him, thus injures his pride and insists that he should get his due. He also makes it heard that Agamemnon doesn't deserve greater rewards because he has least risk at stake. But in the film, (though part of the reason is still he deserves Briseis because his team got her) it is more of it is Briseis per se that Achilles wants. There has been an emotional involvement in the film. It can be supported by scenes wherein Achilles desired to leave the battle behind and forget about the “glory” after what happened between him and the Trojan royalty (wherein in the book he wanted to live a simple life that is why he decides to sail home but of course the reason to see Agamemnon fall is still included). This shows that she became the key to his change in character. He even said it himself at the end, when he told Briseis “You showed me peace in a lifetime of war”. He also asked the Myrmidons to save themselves and sail home while he chose to stay behind. His stay is meant to save Briseis from the fall of Troy as the film has showed and once again the Trojan priestess was used to put into story Achilles' death.
Another is the roles of the gods. In the film the mythological side was limited to omens, compared to the book where they almost control the turnout of the mortals' clash. Other changes are rather less significant and I think was just made to sharpen the drama of the film. In the book, Paris has always been on the battlefield but with a brew of cowardice, it also showed how the early period looks on cowardice. He is usually chastised by Hector and Helen. But the film made Hector more of a loving brother always ready to fight for his brother and Hector's death caused Paris to be brave and took responsibility of defending Troy and their family.
On the film, Agamemnon was very fierce and arrogant, he never initiated agreement with Achilles unlike in the book. He never accepts defeat unlike in the book wherein he even cried and suggested to sail back home.
Another significant character is Patroclus who in the book is just a close friend of Achilles while on the film he is his cousin which gives the reason of Achilles' outrage on his death. From the start it has always been emphasized how protective Achilles is as an Uncle.
Lastly, the survivor Aeneas who carried the continuity of Troy as a race. In the film, his existence was not totally integrated, he was just a simple villager whom Paris entrusted the sword of Troy. While in the book he is a great fighter qualified to really be the next protection of Trojans.
The book showed the connection of the mythological disputes in the changes in the war. They even appear in the battlefields and engage in petty arguments with other gods. But in the film the story is modernized in the sense that magical parts are deleted. Like the talking horses in book 19, the armors that has an aura of their own and the likes. The mythology has been limited to omens and temples only.
The book and the film also celebrates war. The importance of the people were measured in their valuability in the battlefield. It can also be seen how the heroes became mightier in sacrificing long life with their love ones for the glory of dying in the battlefield. It is demonstrated by Achilles and Hector. Though Hector know that he will be killed he still faced Achilles in spite his want to stay with Andromache and watch Astyanax grow handsome. Achilles also chose the glory and honor the great war will give him despite his knowledge that it will also be his doom.
In the tenth and final year of the Trojan War, Chryses, a priest of Apollo, attempts to ransom his daughter from Agamemnon, commander-in-chief of the Achaeans, who has taken her captive while on a raid. When Agamemnon treats him roughly and refuses the ransom, Apollo is angered and brings plague on the Achaeans. The Achaean prophet Calchas correctly identifies the cause of the problem, and he suggests giving the girl back with gifts to Apollo. Agamemnon demands that he be compensated for the loss of the girl, and Achilles, the greatest Achaean warrior, objects. The two men quarrel viciously. Agamemnon says he will take back Briseis, a captive woman who was given to Achilles as a prize for valor. Horribly dishonored, Achilles returns to his ships and refuses to fight. Agamemnon has Briseis taken from Achilles, and he returns Chryses' daughter to him. Achilles asks his mother, the goddess Thetis, to prevail on Zeus, king of the gods, to bring ruin on the Achaeans as long as Achilles does not fight for them. Zeus is indebted to Thetis, and he grants her request.
With Achilles out of the way, Hector, champion of the Trojans, drives the Achaeans back to their beached ships. The Achaeans build fortifications, but at the urging of the chieftains Agamemnon sends and embassy to ask Achilles to return to battle. Agamemnon offers rich prizes, but Achilles refuses the offer and remains withdrawn from battle.
The Achaean fortifications are breached, and many of the greatest remaining Achaean warriors are wounded. Achilles beloved companion, Patroclus, begs Achilles to do something to help their fellow soldiers. He asks that he be allowed to put on Achilles' armor, so that the Trojans will think that Achilles has returned. Achilles grants the request, but warns Patroclus to return once he has driven the Trojans back from the ships. Patroclus drives the Trojans back all the way to their own city walls, but there Hector kills him with the help of Apollo. Hector strips his armor and puts it on himself, and the Achaeans barely manage to save Patroclus' body from desecration.
Achilles goes berserk with grief and rage. Thetis warns him that if he kills Hector, he will die soon afterward. Achilles accepts his own life as the price for revenge. He reconciles himself to Agamemnon, receives new armor, via his mother, forged by the smith of the gods, Hephaestus. He charges into battle, slaughtering Trojans left and right, routing the Trojan army almost single-handedly. He meets Hector, chases him around the city, and kills him easily. He then drags the body from the back of his chariot, running laps around the city of Troy so that the Trojans can watch as their champion's body is horribly desecrated.
Achilles returns to the Achaean camp, where he holds magnificent funeral games for Patroclus. He continues to abuse Hector's corpse. Zeus sends Thetis to tell Achilles that he must accept the ransom that Priam, king of Troy and father of Hector, will offer in exchange for Hector's body. Priam himself comes to see Achilles, the man who has slaughtered so many of his sons, and Achilles suddenly is reminded of his own fatherwho, as Priam has, will outlive his most beloved son. He understands what he has done, and his rage and grief give way to compassion. He returns the body and offers a cease-fire so that the Trojans can bury Hector. With the word of Achilles as their guarantee, the Trojans take eleven days to give Hector a proper mourning and funeral. As the epic ends, the future is clear: Achilles will not live to see the fall of Troy, but the city is doomed nonetheless. All but a handful of her people will be slaughtered, and the city will be wiped off the face of the earth.
The Death of Achilles
In the final books of The Iliad, Achilles refers frequently to his imminent death, about which his mother, Thetis, has warned him. After the end of the poem, at Hector’s funeral feast, Achilles sights the beautiful Polyxena, the daughter of Priam and hence a princess of Troy. Taken with her beauty, Achilles falls in love with her. Hoping to marry her, he agrees to use his influence with the Achaean army to bring about an end to the war. But when he travels to the temple of Apollo to negotiate the peace, Paris shoots him in the heel—the only vulnerable part of his body—with a poisoned arrow. In other versions of the story, the wound occurs in the midst of battle.
The Fall of Troy
The Achaean commanders are nearly ready to give up; nothing can penetrate the massive walls of Troy. But before they lose heart, Odysseus concocts a plan that will allow them to bypass the walls of the city completely. The Achaeans build a massive, hollow, wooden horse, large enough to hold a contingent of warriors inside. Odysseus and a group of soldiers hide in the horse, while the rest of the Achaeans burn their camps and sail away from Troy, waiting in their ships behind a nearby island.
The next morning, the Trojans peer down from the ramparts of their wall and discover the gigantic, mysterious horse. They also discover a lone Achaean soldier named Sinon, whom they take prisoner. As instructed by Odysseus, Sinon tells the Trojans that the Achaeans have incurred the wrath of Athena for the theft of the Palladium. They have left Sinon as a sacrifice to the goddess and constructed the horse as a gift to soothe her temper. Sinon explains that the Achaeans left the horse before the Trojan gates in the hopes that the Trojans would destroy it and thereby earn the wrath of Athena.
Believing Sinon’s story, the Trojans wheel the massive horse into the city as a tribute to Athena. That night, Odysseus and his men slip out of the horse, kill the Trojan guards, and fling open the gates of Troy to the Achaean army, which has meanwhile approached the city again. Having at last penetrated the wall, the Achaeans massacre the citizens of Troy, plunder the city’s riches, and burn the buildings to the ground. All of the Trojan men are killed except for a small group led by Aeneas, who escapes. Helen, whose loyalties have shifted back to the Achaeans since Paris’s death, returns to Menelaus, and the Achaeans at last set sail for home.