'Army of the Lord' in the Bible

And he said, Nay; but as captain of the army of the LORD am I now come. And Joshua fell on his face to the earth, and did worship, and said unto him, What says my lord unto his servant?

They mourned and wept, and then decided to fast until dusk for Saul, for his son Jonathan, for the army of the LORD, and for the house of Israel, because they had fallen in battle.