The Philistines were concerned when David came to rule over a united Israel.1 When he was king only of Hebron, his power was limited and he was not a real threat to Philistine interests.2 Now, however, with David as the head of a united kingdom, Israel was a threat once again. As such, it made sense for them to act quickly before the armies of Israel were prepared and their unity was strengthened. If they could get rid of David, there would be no leader to unite the tribes, and the land of Israel would be theirs for the taking.
17 When the Philistines heard that David had been anointed king over Israel, all the Philistines went up to search for David. But David heard of it and went down to the stronghold.