Eris the goddess of strife was offended that she had not been invited to the wedding of Peleus and Thetis. In revenge, she threw down a golden apple inscribed with the words 'to the fairest', knowing that this would cause an argument amongst the other goddesses. Aphrodite, Hera and Athena all asked Zeus to decide to whom the apple belonged. Zeus did not want to cause any more trouble. He knew that by choosing one of the goddesses he would incur the resentment of the other two. Instead he decided that the mortal Paris should decide.
All three goddesses appeared before Paris. All three goddesses promised Paris different prizes if he picked them. Aphrodite promised him the most beautiful woman in the world. This woman was Helen, the wife of King Menelaus of Sparta. Aphrodite made Helen fall in love with Paris. The couple ran off together. Menelaus called together his allies in Greece. They set off to recapture Helen. The resulting war lasted for ten years.