The soldiers that God is sending to attack Babylon are spoken of as if they were weapons in God's hands. "Indignation" is a metonym for the punishment that God will inflict on Babylon because he is indignant. Alternate translation: "the army that he will use to punish Babylon" (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-metonymy]])