When the towers fall "When the mighty fall" - מגדלים migdalim, μεγαλους, Sym.; μεγαλυνομενους, Aquila; רברבין rabrebin, Chard.; all signifying mighty sizes.
In the day of the great slaughter - When the enemies of the people of God shall have been destroyed - probably in a time subsequent to the slaughter of the army of the Assyrians.
When the towers fall - The towers of the enemy; perhaps referring here to the towers of Babylon. After they should fall, the Jews would be favored with the time of prosperity to which the prophet here refers.