'Groups' in the Bible

So Joab son of Zeruiah and David’s soldiers marched out and met them by the pool of Gibeon. The two groups took up positions on opposite sides of the pool.

Dividing his forces into three groups, he set Joab as commander of one third of his army, Zeruiah's son Abishai, Joab's brother, as commander of another third, and Ittai from Gath as commander of another third. The king informed the army, "I'm going out to battle with you, too."