Question

What help does akhilleus agree to offer the greeks before he reenters battle himself?

Answer 1

He decides to let Patroclus wear his armor

He didn't want to fight so he let Patroclus in disguise lead his army. Patroclus made a mistake however since he didn't just return as he said he would after the defense of the beaches but rather he pushed towards the gates where he died because of this and when his armor was removed everyone saw that it wasn't Achilles.