2 Samuel 5 and 6

In verse 5:3 it reads:
So all the elders of Israel came to the king at Hebron. King David made a covenant with them at Hebron in the Lords presence, and they anointed David king over Israel. That was the 3rd time David has been anointed. 1. Samuel anointed him with his family 2. The tribe of Judah anointed him publicly 3. and now he has been anointed at Hebron.
Verse 5:17-20
When the philistines heard that David had been anointed king over Israel, they all went in search of David, but he heard about it and went down to the stronghold. Then David inquired of the Lord: "should I go to war? will You hand them over to me?" The Lord replied to David, "Go for I will hand them over to you." So David went to Baal-perazim and defeated them there and said, " like a bursting flood the Lord has burst out my enemies before me." Therefore he named that place the Lord bursts out. So why where the philistines not afraid of David, this must have been the Lords way of destroying the philistines.