So the woman replied, "Watch this! His head will be thrown to you over the city wall." Then the woman wisely went back to her people. They cut off the head of Bichri's son Sheba and threw it out to Joab, so Joab sounded his battle trumpet and they withdrew from the city. Everybody went back home and Joab returned to the king at Jerusalem.

if the king starts to get angry and asks you, "Why did you get so near the city to fight? Didn't you know they would shoot from the wall?

All of the men who had accompanied Joab arrived and besieged Sheba in Abel of Beth-maacah. They threw up a siege ramp against the city rampart and began to batter the wall to demolish it.