One day Zeus threw huge party on Mount Olympus he invited all the gods & goddess except Eris the goddess of personified of spirit. 

So she seeks for revenge she made a golden apple. An apple for the fairest. Athena, Hera,Aphrodite fight because they want to know who's the fairest. Zeus can't choose because the three of them are beautiful. So the three goddess decides to ask an mortal a Trojan prince name Paris the three goddess offered him anything he wants but Paris choose Aphrodite gift Aphrodite promise that she will give him beautiful woman name Helen  the most beautiful around the world. Paris getting his promise stole Helen away from Sparta which led to World War 1 blush these allies include Odysseus, Agamemnon, Ajax and Achilles the conflict last a full decade with Troy placed under siege for the last 9 years. Odysseus wants to go home with his wife Penelope. Odysseus had great plan to build a Big Wooden horse  to end the war.

Incident 1 Choosing Helen 

Because of Paris's obsession with the woman name Helen lead to the Trojan war. Trojan people and Greek people fought each other and created a large conflict.

Incident 2   A Madman Kills and Disgraces Hector

 Achilles met Hector in single combat and killed him. Then, in his madness and grief over Patroclus, Achilles dishonored the Trojan hero's body by dragging it around the ground tied to his chariot by a belt. This belt had been given Hector by the Achaean hero Ajax in exchange for a sword. Days later, Priam, Hector's aged father and the king of Troy, persuaded Achilles to stop abusing the body and return it for proper burial.

Incident 3 The Achilles Heel

Soon after, Achilles was killed, wounded in the one spot where legend tells us he was not immortal--his heel. When Achilles was born, his mother, the nymph Thetis, had dipped him into the river Styx to confer immortality, but the spot where she held him, his heel, remained dry. Paris is said to have hit that one spot with his arrow, but Paris wasn't that good a marksman. He could only have hit it with divine guidance--in this case, with the help of Apollo.