There was war again: and David went out, and fought with the Philistines, and killed them with a great slaughter; and they fled before him.
"And there was war again"  (1 Samuel 19:8).  This war, like many others, was with the Philistines.  This is not a reference to the conflict in which David defeated Goliath, but to one of the campaigns of that long struggle of the Philistines against Saul's government that finally resulted in its overthrow, ending in Saul's death.  David trusted the solemn oath Saul had sworn to the effect that he should not be put to death; and for some extended time everything seemed to be back to normal.