The fleet, numbering 1 200 ships, assembled at the port of Aulis in Boeotia.
He foretold the duration of the siege of Troy, and, when the fleet was detained by adverse winds at Aulis, he explained the cause and demanded the sacrifice of Iphigeneia.
They were famous in the ancient world for their maiden goddess, identified by the Greeks with Artemis Tauropolos or Iphigeneia, whom the goddess was said to have brought to her shrine at the moment when she was to have been sacrificed at Aulis.
The Catalogue of the Ships begins with Boeotia; the list of Boeotian towns is much the longest; and they sail, not from the bay of Argos, but from the Boeotian harbour of Aulis.
On the eve of sailing from Aulis he attempted to offer a sacrifice, as Agamemnon had done before the Trojan expedition, but the Thebans intervened to prevent it; an insult for which he never forgave them.