Saul was at first unsure how to act. He calls for the ark of God to make enquiries via the priest.
There is a very obvious change in fortunes of the battle, and everyone sees it. There had been some Hebrews who in their fear had gone to fight with what they thought was the winning side, the Philistines, the vastly greater side numerically. These now change their minds and desert to the Philistines and come back to where they should have been all along. That was far from the type of soldier that Israel needed fighting on their side. We should fight for the Lord, like Jonathan and his armour bearer, even though we are massively outnumbered, because we believe that God can give the victory to few as well as to many. We do not change sides in a cowardly way as the fortunes of the battle waver. We are to be people of principle who know what they believe. The church needs people of deep conviction.