It happened in those days, that the Philistines gathered their hosts together for warfare, to fight with Israel. Achish said to David, Know you assuredly, that you shall go out with me in the host, you and your men.
"Philistines gathered their forces ... to fight against Israel"  (1 Samuel 28:1).  This was far more than an ordinary mobilization for war, because, "On this occasion they sent to all their confederates that they would go along with them to the war."[1]