11And the next day Saul put the people in three companies. And they came into the midst of the camp in the morning watch and struck down the Ammonites until the heat of the day. And those who survived were scattered, so that no two of them were left together.
The division into three groups looks back to Gideon (Judges 7:16).1 It was a common military practice at the time to break up an army when marching to battle so that if the army was ambushed, only one section (and not the entire army) would be destroyed.2
11 And the next day Saul put the people in three companies. And they came into the midst of the camp in the morning watch and struck down the Ammonites until the heat of the day. And those who survived were scattered, so that no two of them were left together.