What does Isaiah 13:16 mean?

Isaiah does not shy away from predicting what will happen to the people of Babylon when the Lord's judgment comes. The armies the Lord has summoned will attack the city and invade it (Isaiah 13:2–5). There will be no difference for those who run or those who stay behind (Isaiah 13:12–15). The cruel and ruthless soldiers will carry out utter destruction without mercy. The scenes are grotesque, with gut-wrenching imagery meant to inspire a sense of horror. Infants will be murdered in view of their parents. The treasures of their homes will be carried off. The wives of the men of Babylon will be raped.

Though God was the one who arranged for Babylon to fall to foreign armies (Isaiah 13:6), He is not directing these specific acts to occur. The deeds, themselves, were common in warfare of the ancient world. In fact, part of God's judgment on that nation comes as they experience what they inflicted on others to gain dominance. Those who kill the innocent, because they do not value them, often live to see their own innocent loved ones destroyed in the same way. Babylon, itself, was used as a tool to punish Assyria (Isaiah 10:12–14), and so will be judged for their own sins. Likewise, those who conquer Babylon will answer to God for their actions.

In all this misery, the Babylonians will be crushed to realize that their false gods cannot protect or save them. The message written to Israel is clear. They are to trust in the Lord, and in Him alone, to protect them. He is their only hope to escape the slaughter that comes for those who become the object of the Lord's anger.