What was the kindness Nahash had showed David in chapter nineteen?
We are not told. Perhaps, after David’s coronation, Nahash believed David was someone he could work with and effected a treaty. We simply don’t know.
In any case, upon Nahash’s death, David sent a diplomatic delegation to his son Hanun. The delegation was shamefully treated and this episode helps us to see the cementing of David’s power.
In the reading, don’t miss the progression of the story, which has a particular formula. When the Ammonites saw (vs. 6) that David was insulted, they gathered mercenary soldiers to help them. When Joab saw (vs. 10) the armies arrayed against his own, he divided his forces, formulated a plan, and left the success in the hands of the Lord. When the Arameans saw (vs. 16) they had been defeated by a smaller army, they called for reinforcements. When the Arameans saw they had been defeated by Israel, they made peace with David (vs. 16) and became subject to him.
Notice how the story shifts from the Ammonites, who could have never defeated David, to the Arameans (Syrians) who should have been able to defeat him. No one can. God is on His side.
Though we should regard every battle as the Lord’s, success will seldom come without our own planning and involvement. If this is true, why should we say it’s in the Lord’s hands if, in fact, it is in our own? Note the Syrians planned too, and had a superior force, but they could not defeat the Lord, and we cannot win our battles without Him.