It was so on the next day, that Saul put the people in three companies; and they came into the midst of the camp in the morning watch, and struck the Ammonites until the heat of the day: and it happened, that those who remained were scattered, so that no two of them were left together.
The deployment of the forces of Israel in three companies was very similar to the actions of Gideon in  Judges 7:16f, as was also their attack in the third watch of the night, between two o'clock and six o'clock in the morning.