The Achaean fleet consisted of more than a thousand ships gathered at Aulis. But the wind had completely died and navigation was impossible. The prophet Calchas stated that the goddess Artemis caused this as punishment for the death of the sacred deer by Agamemnon, in his attempt to prove that he was a better hunter. The only way to appease Artemis, according to Calchas, was to sacrifice the daughter of Agamemnon and Clytemnestra, Iphigenia. Agamemnon initially refused, but the rest of the Achaeans leaders threatened to set Palamedes the leader of the campaign, so he eventually declined. Trying to lure Iphigenia to come at Aulis, Agamemnon sent the happy news that she was to come and marry the bravest of the Achaeans, Achilles. Iphigenia rushed with her mother Clytemnestra without knowing her fate.
Finally, Iphigenia, agreed to do the will of her father while Clytemnestra never forgave Agamemnon. Just before the sacrifice of Iphigenia, Artemis intervened and transferred her to a distant place, where she served as a priestess of the goddess.
Agamemnon, seeing that his daughter disappeared by supernatural means, following the advice of Calchas, sacrificed a lamb. Both were the only ones who knew that Iphigenia was not really sacrificed. A human sacrifice would be the biggest insult in the faith of the ancient Greeks.