And Joab fought against Rabbath of the children of Ammon, and laid close siege to the royal city.

And Joab fighteth against Rabbah of the Bene-Ammon, and captureth the royal city,

Now Joab was fighting against Rabbah, in the land of the children of Ammon, and he took the water-town.

And then Joab fought against Rabbah of the sons of Ammon, and he fought outside the royal city.

And took the royal city - How can this be, when Joab sent to David to come to take the city, in consequence of which David did come and take that city? The explanation seems to be this: Rabbah was composed of a city and citadel; the former, in which was the king's residence, Joab had taken, and supposed he could soon render himself master of the latter, and therefore sends to David to come and take it, lest, he taking the whole, the city should be called after his name.

And Joab fought against Rabbah of the children of Ammon,.... Of his being sent against it, and of his besieging it, we read in 2-Samuel 11:1; but it can hardly be thought that he had been so long besieging it, as that David had two children by Bathsheba; but the account of the finishing of it is placed here, that the story concerning Bathsheba might lie together without any interruption:
and took the royal city; or that part of it in which the king's palace was, and which, as Abarbinel observes, was without the city, as the palaces of kings now usually are.

To be thus severe in putting the children of Ammon to slavery was a sign that David's heart was not yet made soft by repentance, at the time when this took place. We shall be most compassionate, kind, and forgiving to others, when we most feel our need of the Lord's forgiving love, and taste the sweetness of it in our own souls.

RABBAH IS TAKEN. (2-Samuel 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.

Conquest of Rabbah, and Punishment of the Ammonites (comp. 1-Chronicles 20:1-3). - "Joab fought against Rabbah of the children of Ammon, and took the king's city." המּלוּכה עיר, the capital of the kingdom, is the city with the exception of the acropolis, as 2-Samuel 12:27 clearly shows, where the captured city is called "the water-city." Rabbah was situated, as the ruins of Ammn show, on both banks of the river (Moiet) Ammn (the upper Jabbok), in a valley which is shut in upon the north and south by two bare ranges of hills of moderate height, and is not more than 200 paces in breadth. "The northern height is crowned by the castle, the ancient acropolis, which stands on the north-western side of the city, and commands the whole city" (see Burckhardt, Syria ii. pp. 612ff., and Ritter, Erdkunde xv. pp. 1145ff.). After taking the water-city, Joab sent messengers to David, to inform him of the result of the siege, and say to him, "Gather the rest of the people together, and besiege the city (i.e., the acropolis, which may have been peculiarly strong), and take it, that I may not take the city (also), and my name be named upon it," i.e., the glory of the conquest be ascribed to me. Luther adopts this explanation in his free rendering, "and I have a name from it."

Royal city - That is, that part of the city where was the king's palace; though now it seems he was retired to a strong fort.