It happened, at the time of the return of the year, at the time when kings go out [to battle], that Joab led forth the army, and wasted the country of the children of Ammon, and came and besieged Rabbah. But David stayed at Jerusalem. Joab struck Rabbah, and overthrew it.
In bringing these battle stories together, the writer has omitted a number of passages from the parallel section of 2 Samuel. He is concerned with God’s plan for establishing the kingdom of David, not with the fate of Saul’s survivors (2 Samuel 9:1-13; 2 Samuel 21:1-17), nor with David’s personal sins and family troubles (2 Samuel 11:2-25; 2 Samuel 13:1-26).