John Gill Commentary 2 Samuel 11:20

"it shall be that, if the king`s wrath arise, and he say unto thee, Wherefore went ye so nigh unto the city to fight? knew ye not that they would shoot from the wall?" — 2 Samuel 11:20 (ASV)

And if so be that the king's wrath arise
Which might be seen in his countenance, or expressed in his words:

and he say, wherefore approached ye so nigh unto the city when ye did
fight ?
as to expose the king's troops to the enemy on the wall, who by stones or darts greatly annoyed them, or sallied out on them, and killed many of them:

knew ye not that they would shoot from the wall ?
they must have known that, and therefore should have kept out of the reach of their shot.