Charles Ellicott Commentary 2 Samuel 12:26

"Now Joab fought against Rabbah of the children of Ammon, and took the royal city." — 2 Samuel 12:26 (ASV)

Took the royal city. — The parallel narrative is resumed at this point in 1 Chronicles 20:2. Rabbah was situated in the narrow valley of the upper Jabbok, on both sides of the stream, but with its citadel on the cliff on the northern side. The “royal city” of this verse, and “the city of waters” of the next, refer probably to the city proper, while the “city” of 2 Samuel 12:28–29 is no doubt the citadel, which was more strongly fortified.