During the Trojan War, Agamemnon was forced to give up his concubine, Chryseis.  As recompense, Agamemnon took Briseis, a concubine of Achilles.  With his pride now injured, Achilles refused to fight.  Achilles' mother, Thetis, went to Zeus for help.  In order that her son should receive more glory, she persuaded him to cause the Trojans to win, until the Greeks would beg Achilles to return to the battle.


  1. HomerIliad.