2 Samuel 2:12

Abner … went out. This is a further proof of considerable success on Abner's side. Encouraged by the result of numerous skirmishes with the Philistines, and the gradual restoration of the king's authority in Ephraim and Benjamin, Abner determined to make the attempt to win back Judah also. There David had been content with protecting Judah, and establishing good order; and, following his constant custom, had taken no steps to obtain for himself the kingdom "over all Israel." The war was of Abner's choosing, and shows him to us in the character of an able but ambitious and restless man.