The rush to defend comes too late (Nahum 2:5). The defenses are already breached.
Nineveh had a reservoir created by a double dam on the Khosr River, a tributary of the Tigris that flowed through the city. The reservoir was enhanced by a series of flood gates.
The Greek historian Diodorus reported that a great amount of rain had already swollen the city’s river system. By first closing, then opening the flood gates, Nineveh’s attackers released the stored water as a battering ram against the city walls.