What does Isaiah 13:5 mean?
The Lord is describing the vast army He has assembled to rain down the anger of His judgment against Babylon. This is an army that He has set aside for this attack. It is huge, it is loud, and it includes troops from many nations that have gathered (Isaiah 13:3–4).Now the Lord adds that these are not local nations. Some have traveled great distances to participate in this attack. They have come from the "end of the heavens," This means they have come as far away as the sky reaches. They have all come because the Lord wants them there. They are the weapons of His indignation or anger. He will wield these nations to destroy the entire land of Babylon.
Nothing God has revealed so far means these armies have any concept they are fighting the Lord's holy battle against the arrogant king of Babylon. In their minds, they have come for other purposes. They will act according to their own choices—some of which will be atrocities that God will also punish as sin (Isaiah 13:16; Mark 4:22; Matthew 12:36). The greater message is that the God assembles armies and gives victories. There is nothing outside of His influence.