In the tenth year of the Trojan War, tensions are running high among the Achaians (a super-ancient name for the Ancient Greeks). First, the priest Chryses comes to ask their leader, King Agamemnon, to release his daughter, whom Agamemnon was holding captive. When Agamemnon refuses, the priest prays to the god Apollo to send a plague against the Achaians.

After nine days of plague, the Achaians assemble again and demand that Agamemnon give the girl back. Agamemnon eventually agrees, but only if he gets to take Briseis, the girlfriend of Achilleus, the greatest warrior of the Achaians. Even though Achilleus gives her up, he becomes so enraged that he refuses to fight any more. That and he prays to his mother, Thetis, who happens to be a goddess, to pull some strings with the other gods so that the Achaians will start getting defeated in battle and realize how much they depend on him.

Achilleus's mom definitely spoils him. She gets Zeus, the king of the gods, to agree to Achilleus's request. Sure enough, the next day the Trojans make a successful counterattack, led by Hektor, their greatest warrior. Several days of violent fighting follow, at the end of which the Trojans have the Achaians pinned against the beach, and are threatening to burn their ships.

The Iliad by Homer