“Let the sons of the Achaeans, say I, fight fasting and without food, till we have avenged them; afterwards at the going down of the sun let them eat their fill.”
~ The Iliad - Book XIX (Samuel Butler Translation. p139 / v200)
Thetis gives Achilles the newly forged armor. He is ready to fight. Ulysses asks for time to rest and food for the army. Agamemnon reconciles and gives gifts to Achilles including Briseis. Briseis cries over Patroclus’ body. Achilles gets ready to fight.
In Book 19 of The Iliad, Achilles is raring to go and says that the army must attack the enemies immediately to avenge Patroclus. Ulysses mentions that the men are tired, and it may be better for them to eat first and then go into battle. There is back and forth, but Achilles decides to stay hungry until he avenges his comrade.