And it came to pass, that after the year was expired, at the time that kings go out to battle, Joab led forth the power of the army, and wasted the country of the children of Ammon, and came and besieged Rabbah. But David tarried at Jerusalem. And Joab smote Rabbah, and destroyed it.
At the time that kings go out to battle - in spring, the usual season, in ancient times, for entering on a campaign; i:e., a year subsequent to the Syrian war. Joab led forth the power ... and wasted the country ... of Ammon. The former campaign had been disastrous, owing chiefly to the hired auxiliaries of the Ammonites; and as it was necessary, as well as just, that they should be severely chastised for their wanton outrage on the Hebrew ambassadors, Joab ravaged their country, invested their capital, Rabbah, and having, after a protracted siege, taken one part of it, the lower town or 'city of waters,' insulated by the winding course of the Jabbok, he, knowing that the fort called 'the royal city' would soon fall, invited the king to come in person, and have the honour of storming it. The knowledge of this fact (mentioned 2 Samuel 12:26) enables us to reconcile the two statements, "David tarried at Jerusalem" (1 Chronicles 20:1), and "David and all the people returned to Jerusalem' (1 Chronicles 20:3).