Meanwhile, Joab fought against Rabbah of the Ammonites and captured the royal fortress.
We have here an account of the conquest of Rabbah, and other cities of the Ammonites. Though this comes in here after the birth of David's child, yet it is most probable that it was effected a good while before, and soon after the death of Uriah, perhaps during the days of Bath-sheba's mourning for him. Observe, 1.
Commenting on 2 Samuel 12:26-31
And Joab sent messengers to David,.... To acquaint him how he had proceeded, and what success he had had: and said, I have fought against Rabbah; laid siege to it, and skirmished with parties that sallied out upon them: and have taken the city of waters; the same with the royal city, and so the Targum here renders it; so called because situated by the...
RABBAH IS TAKEN. (Sa2 12:26-31) Joab fought against Rabbah--The time during which this siege lasted, since the intercourse with Bath-sheba, and the birth of at least one child, if not two, occurred during the progress of it, probably extended over two years.