In Greek myth, Achilles is the legendary but reluctant warrior who fought in the Trojan War. His mother, Thetis, who dipped him in the river Styx after he was born, rendered him nearly impervious to harm by this action. However, she had to hold onto his heel in order to retrieve him from the water, thus missing a spot. The only way Achilles could be killed was by injury to his heel. This leads to the now famous expression, "Achilles’ heel," meaning a person’s major weak point.
The story of Achilles figures largely in Homer’s Iliad. He is first introduced as having withdrawn from the war in a fight with Agamemnon over the capture of several Trojan women. It is important to understand his reluctance to engage in the battle. It is prophesied before Achilles leaves for Troy that he will die there. Thus he is necessarily loath to take part in the battle in any case.
However, the quarrel is forgotten after the Trojans kill the best friend of Achilles, Patroclus. The death spurs him to action and he rushes to battle, with great might and purpose. He kills Hector, but is then killed by Paris, thus fulfilling the prophecy regarding his fate.
Achilles also meets with Odysseus in Homer’s Odyssey and in lengthy speech declaims the war and places value on how much more important life is than valor. It is a suitably tragic statement and may have been inspired by Homer’s observation that, while warfare existed somewhat constantly, some men simply did not want to participate.
Some analysts of mythology have claimed that Achilles’ real "heel" is pride, friendship, or anger. Had his anger not been provoked by the death of Patroclus, he might not have rushed into battle. However, others point to the story of Achilles as yet another lesson of fate as understood by the Greeks. Like Oedipus, he rushes toward a fate that is not within his control. He cannot escape from his destiny, anymore than Oedipus can escape from the horrible act of slaying his father and marrying his mother.