If mere men could be considered responsible for Saul and David’s success, those men would be Abner and Joab. With the death of Abner and Saul, it left a power void because David had not yet been made king of all Israel.
It would appear that two other men would be contenders for Saul’s throne: Ish-Bosheth, Saul’s son, and Mephibosheth, his grandson). Chapter four tells us how they came to be eliminated. Mephibosheth was a cripple. Ish-bosheth was murdered.
Recab and Baanah expected to be rewarded for eliminating David’s competition for the throne, but they were tragically mistaken. David would not raise his hand against God’s anointed. He punished others who did. David was horrified at Saul’s blood letting against the Gibeonites – a story as yet untold and only referred to in chapter 21. For a king who himself was criticized for bloodshed (1 Chronicles 22:8), David was remarkably sensitive to it – in a good way. It will surprise us then, as the story continues, that David can be so blind to violence in his own house among his own children.