According to the Iliad, the Trojan War was initiated by the abduction of Helen, the queen of Sparta, by Paris, a Trojan prince.
Paris and Helen's entanglement began when Paris was called upon by the goddesses Hera, Athena, and Aphrodite to judge a contest between them. The goddess Eris, who loves chaos, rolled a golden apple into the midst of the goddesses, knowing they would fight over who it was intended for. The goddesses ask Paris to determine which of the three of them is worthiest of the apple, since he has a reputation for fairness. However, the contest is marked by bribery: Hera promises Paris an empire; Athena promises him military prowess; Aphrodite promises him the most beautiful woman in the world. This woman happens to be Helen, the queen of Sparta. Paris goes with Aphrodite, who causes Helen to fall madly in love with Paris due to an arrow from Eros. Paris spirits Helen away on a ship headed for Troy.
This kidnapping enrages Helen's husband, Menelaus, the king of Sparta. With Paris being unwilling to return Helen to her family in Sparta, Menelaus calls on his brother Agamemnon for aid, and in turn, Agamemnon calls on other kings. Forming an alliance, they wage war on the Trojans, beginning the years-long struggle of the Trojan War.