And it came to pass, after the year was expired, at the time when kings go forth to battle, that David sent Joab, and his servants with him, and all Israel; and they destroyed the children of Ammon, and besieged Rabbah. But David tarried still at Jerusalem. When kings go forth - This was about a year after the war with the Syrians spoken of before, and about the spring of the year, as the most proper season for military operations. Calmet thinks they made two campaigns, one in autumn and the other in spring; the winter being in many respects inconvenient, and the summer too hot.
Related Commentaries of 2 Samuel 11:1
2 Samuel 11:1
1 And it came to pass, after the year was expired, at the time when kings go forth to battle, that David sent Joab, and his servants with him, and all Israel; and they destroyed the children of Ammon, and besieged Rabbah. But David tarried still at Jerusalem.