The battle fought by God against the Babylonians is described as him piercing their warriors with their own swords. He worked against them in such a way that they turned upon themselves and attacked each other bringing about their own deaths. It is as if instead of them shooting the Israelites, they shot themselves. The Babylonians stormed out like a whirlwind to engage the Israelites in combat. They entered the battle confident and assured of being victorious as is shown by the words rejoicing as if to devour the poor in secret.
Just as they had defeated other armies, they entered the battle against the Israelites with a spirit of joyful confidence being assured of victory, thinking that their enemy would not be strong enough to stand up against them.
14 You pierced with his own arrows the heads of his warriors, who came like a whirlwind to scatter me, rejoicing as if to devour the poor in secret.