Albert Barnes Commentary 1 Kings 20:14

"And Ahab said, By whom? And he said, Thus saith Jehovah, By the young men of the princes of the provinces. Then he said, Who shall begin the battle? And he answered, Thou." — 1 Kings 20:14 (ASV)

The princes of the provinces are the governors of districts, many of whom may have fled to the capital as the hostile army advanced through Galilee and northern Samaria. The young men are their attendants, youths unaccustomed to war.

Who shall order the battle? That is, "Who shall join the battle and begin the attack? We or the enemy?" The reply was that the Israelites were to attack.