5.25 2 Samuel -- David's Wars
David pursued an aggressive, even ruthless, foreign policy. He fought in succession Philistia, Moab, Syria, Ammon, Edom and Amalek. In regard to Moab,
David also defeated the Moabites. He made them lie down on the ground and measured them off with a length of cord. Every two lengths of them were put to death, and the third length was allowed to live (2 Sam 8:2).
This is today considered a war crime, an atrocity. These men were not killed in battle, but as prisoners of war. We can, perhaps, measure the hardness of the man by the relative percentages of those he killed versus those he spared. Yet even worse: wasn't it Moab that gave refuge to David's parents when Saul was on the warpath? (1 Sam 22:3-4). What justifies such a cruel repayment of their earlier hospitality?
On the other hand, there is the example of his treatment of the Ammonites:
In the course of time, the king of the Ammonites died, and his son Hanun succeeded him as king. David thought, "I will show kindness to Hanun son of Nahash, just as his father showed kindness to me." So David sent a delegation to express his sympathy to Hanun concerning his father (2 Sam 10:1-2).
The foolish young king treated David's messengers shamefully, thus provoking a major war among Ammon, Syria and Israel. But this at least was a conflict that David did not provoke.