He had a disagreement with Agamemnon over a girl.
Agamemnon wanted Achilles' girl (called Briseis) but Achilles refused, and was about to kill Agamemnon in anger, but a goddess stopped him, saying that killing him wouldn't solve anything, so instead he said he would leave the war - stop fighting, and that Agamemnon ould have the girl but would regret it later.
He acted like a child. After hearing that his concubine, Chryseis, needed to be returned to her father (the priest of Apollo) Agamemnon's basic response was that if he had to suffer the loss of a concubine, that Achilles should lose his too. When Achilles became irate over this loss and refused to continue fighting, Agamemnon showed him the door claiming that he could still win without Achilles. Only the death of Achilles's close friend Patroklos inspired Achilles to fight for the Greeks again.
Phthia, as he says in the first book of the Iliad in his rant to Agamemnon.
because Hector killed Achilles' friend Patroclus in a fight, when Patroclus had dressed up as Achilles so he could fight in one of the battles of Troy.(In the film Troy starring Brad Pitt, Achilles and Patroclus were cousins. In the original legends, they were friends but not related)
He had a disagreement with Agamemnon over a girl.
Agamemnon was forced to return his lover Chryseis to end the plague, and took Achilles' concubine Briseis as his own. Enraged at the dishonor Agamemnon had inflicted upon him, Achilles decided he would no longer fight.
Patroclus used Achilles armor to fight Hector when Achilles refused to continue fighting for Agamemnon. Patroclus was Achilles close friend and lover in the Iliad.
Achilles withdraws from battle because Agamemnon offends him by taking his concubine. Achilles states that if Briseis is not returned to him he will not fight.
Agamemnon took the Trojan woman, Briseis, whom Achilles had captured, taken as his slave, and fallen in love with because an oracle had ordered him (Agamemnon) to give up his own woman, Chryseis.
Achilles saw Briseis as his; be it as slave or wife/bride, and when Agamemnon was premitted to take what was Achilles's it said that the others valued him less and so he refused to fight in the war.
Oh honey, Achilles was as justified as a cat in knocking over a vase. Agamemnon done him dirty by taking his girl, so of course he was gonna throw a hissy fit and sit out of battle. Can you blame him? Men and their egos, I tell ya.
Agamemnon wanted Achilles' girl (called Briseis) but Achilles refused, and was about to kill Agamemnon in anger, but a goddess stopped him, saying that killing him wouldn't solve anything, so instead he said he would leave the war - stop fighting, and that Agamemnon ould have the girl but would regret it later.
He was in a hissy fit because his commander King Agamemnon had taken over his girlfriend Briseis.
He acted like a child. After hearing that his concubine, Chryseis, needed to be returned to her father (the priest of Apollo) Agamemnon's basic response was that if he had to suffer the loss of a concubine, that Achilles should lose his too. When Achilles became irate over this loss and refused to continue fighting, Agamemnon showed him the door claiming that he could still win without Achilles. Only the death of Achilles's close friend Patroklos inspired Achilles to fight for the Greeks again.
At the beginning of the selection in Iliad, Achilles is angry with Agamemnon and refuses to fight in the Trojan War, leading to a conflict between the two that sets the stage for the events that follow.
Phthia, as he says in the first book of the Iliad in his rant to Agamemnon.