We usually think of the Trojan War as a story about passion, with Paris and Helen as the spark. I'd like to suggest it's really a story about obligation. Look at why each side is there. Hardly anyone in the Greek camp wants to be at Troy, and the reason they have come is a promise they made years earlier, before anyone knew what it would cost. The war does not begin with a kidnapping. It begins with an insurance policy.
The wedding nobody could snub
Start with the apple. The sea goddess Thetis was marrying a mortal, Peleus, and all the gods were invited except Eris, goddess of strife. She turned up anyway and rolled a golden apple among the guests, marked for the fairest. Hera, Athena and Aphrodite each claimed it. Zeus, wise enough not to decide, handed the judgement to a mortal, Paris, a Trojan prince who was herding cattle on Mount Ida.
This part comes from a lost epic, the Cypria, and I like how petty the cause is. It's an etiquette failure. One guest was left off the list, and the response was to throw a grenade. The war begins because someone felt excluded from a party, which every reader recognises.
The three goddesses each offered a bribe. Hera offered rule over many lands. Athena offered skill in war. Aphrodite offered the most beautiful woman in the world. Paris chose Aphrodite, and the woman was Helen, who was already married to Menelaus of Sparta. Notice that the judgement itself isn't really where the war starts. It's just the thing that makes a particular man willing to take the risk.
The oath
Here is the part I think matters most, and it happened long before the apple. When Helen was a young woman, her stepfather Tyndareus had a problem. Every important prince in Greece wanted to marry her, and he was afraid that whoever he chose would be attacked by the rest. Odysseus, who was one of the suitors, offered a solution, in exchange for help in winning the hand of Penelope. He told Tyndareus to make all the suitors swear an oath to defend the chosen husband against anyone who might try to take Helen away.
They all swore. Helen married Menelaus. It was a clever fix, and it worked perfectly, until Paris carried her off to Troy. At that point the oath came due. Agamemnon, Menelaus's brother, called on the suitors, and the whole of Greece was bound to go.
Think about the irony. The oath was designed to prevent a war. It was supposed to make the princes into a deterrent. Instead, it made the war automatic. And its inventor, Odysseus, was the very man who tried to avoid fighting when it came. When Palamedes arrived at Ithaca to collect him, Odysseus pretended to be mad, ploughing a field and sowing it with salt. Palamedes put the infant Telemachus in front of the plough, and Odysseus turned the blade aside. The trick was exposed. He had to go.
The camp
Once the thousand ships arrive at the Hellespont, the story slows to a crawl. The Greeks sit on the beach for ten years, raiding the surrounding territory and besieging a city they can't take. Homer's Iliad covers only a few weeks in the tenth year, and it begins with a quarrel, not a battle. Agamemnon takes Achilles's prize, a woman named Briseis, and Achilles withdraws from the fighting in a rage.
The same obligations hold the camp together and almost break it. The kings follow Agamemnon because they've sworn. Achilles follows him because he has a reputation to keep. And when Agamemnon breaks the rules of honour by seizing a prize that belongs to someone else, the whole machine nearly stops. Homer is much more interested in what honour demands, and what it costs when it is violated, than in who wins.
The gods on both sides
The gods are also bound by who they owe. Hera and Athena, who lost the apple contest, hate Troy and back the Greeks. Poseidon, who built the walls of Troy and was cheated of his wages, is on the Greek side too. Aphrodite, who won, supports Paris. Apollo and Ares lean toward Troy. Each god has a reason, and almost none of the reasons are about right and wrong. They are about grudges and debts.
Zeus, who loves Troy's king Priam but also owes Thetis a favour, is trapped between them. In the Iliad he is shown trying to stay neutral and failing, and at times he simply forbids the others to interfere, a ban which doesn't last. The king of the gods spends the war trying to balance who owes what to whom.
The poem that stops early
Here's a fact that surprises people the first time they read the Iliad. It doesn't end with the fall of Troy. It doesn't even show it. The poem ends with the funeral of Hector, the Trojan hero, after Achilles has killed him and then, moved by Priam's plea, handed back the body. The wooden horse, the sack of the city, the deaths of Priam and Astyanax all happen in other poems, and in later retellings.
I think that choice is deliberate. Homer stops at the moment when two enemies, bound by their own duties, find a point of shared humanity. Achilles gives Hector's body back because the old man reminds him of his father. For a moment the chain of obligations loosens. And then the poem ends, and everyone knows that it will tighten again.
What stays
So when I think about Troy now, I don't think about a beautiful face. I think about a long chain: a snubbed guest, a bribed judge, a clever oath, a mad king ploughing salt, a stolen prize, a returned body. Almost everyone in the story is doing what they promised, and that's exactly what destroys them. It is a myth about the cost of keeping your word in a world where words are made carelessly.