What caused the Trojan war?

Three goddesses: Aphrodite, Hera, and Pallas Athena, saw a golden apple, and wanted it to be theirs. Whoever was to receive the golden apple, was to be named the "fairest of them all." Zeus, as well as many others, refused to be the judge of this. Paris was an excellent judge of beauty and so it was settled that he would do the job. Paris was amazed at all of the beautiful women, but he ended up choosing Aphrodite. He then gave the golden apple to her, and the Judgement of Paris started the Trojan War.