What shall we do? — Literally, What to do? i.e., What is to be done? what must we do?
The army. — The troop (gĕdûd) of mercenaries.
Related Commentaries of 2 Chronicles 25:9
2 Chronicles 25:9
9 And Amaziah said to the man of God, But what shall we do for the hundred talents which I have given to the armyb of Israel? And the man of God answered, The LORD is able to give thee much more than this.