As long as David is only the king of Judah, the Philistines do not seem upset by his rule. In fact, they may have considered him a vassal king, one step removed from the role he played under Achish as a mercenary commander. But once David becomes king of all Israel, the Philistines realize that he is a threat to their control of the northern parts of Israel (5:17–25). So before David has a chance to get established, the Philistines launch an attack, perhaps even before David has captured Jerusalem. It seems unli…