Answer: Here you go
Explanation: Achilles’ mother, Thetis, a minor sea goddess, knew that her son wouldn’t return from Troy, if he ever went there. Therefore she decided to keep him at all costs away from the war, although he was more than eager to fight and win immortal glory (kleos aphthiton, as Homer would say). She sent him to the island of Scyros, to live among the daughters of King Lycomedes (by the way, Lycomedes was said to have killed Theseus, but that’s another story). Achilles was forced to use the name Pyrrha ‘the red/reddish/auburn (haired) one’ (see this answer for more on that). While there Achilles had at least one son from one of the princesses, Pyrrhos or Neoptolemos.
The Achaeans learned where Achilles was and sent the most cunning among them, Odysseus, to find him and persuade him to join them. Odysseus visited the palace disguised as a merchant and presented the court and the princesses with all sorts of dresses and jewels. He had also an armor and other weapons among the merchandise. Achilles, still disguised as a girl, ignored everything else and started examining the weapons. Then one of Odysseus’ companions blew a trumpet as if there were an attack. The girls panicked and run away, but Achilles immediately took up the weapons and stood his ground. Odysseus didn’t need anything else; he talked to him and persuaded him to join him.
Note that according to the Iliad Achilles knew pretty well that he was destined to die in Troy, so his decision was conscious; he preferred a short but glorious life.