These weren’t just any surrounding nations; these nations each have long histories as adversaries of Israel. Edom, descended from Jacob’s older brother Esau, lost any chance of being God’s chosen people when Esau sold his birthright to Jacob for stew. Moab and Ammon were formed by the descendants of an incestuous relationship between Abraham’s nephew Lot and Lot’s daughters. The Philistines, although not related to the Israelites, were frequent enemies whose military prowess threatened Israelite tribes on many occasions. And the Amalekites, also descended from Esau, were almost constant enemies of the Israelites, employing ruthless tactics in their war mongering. By subduing these nations, David not only secures the safety of Israel, but he reaffirms God’s selection of Israel as His people over all the other nations in the land.