John Calvin on Nahum 3:12

The Prophet here declares that the strongholds of the Assyrians would avail them nothing; whether they trusted in the number of their men, or in their walls, or in other defenses, they would be disappointed; for all things, he says, will of themselves fall, even without being much assailed. And he employs a very apposite similitude, “Thy fortifications,” he says, “which thou thinkest to be very strong, shall be like figs; for when the fruit is ripe, and any comes to the tree, as soon as he touches it or any of the branches, the figs will fall off themselves.” We indeed know that there is not much firmness in that fruit; when it is ripe, it immediately falls to the ground, or if it hangs on the branches, a very little shaking will bring it down. We now see the design of the Prophet.

And hence an useful doctrine may be deduced: whatever strength men may seek for themselves from different quarters, it will wholly vanish away; for neither forts, nor towers, nor ramparts, nor troops of men, nor any kind of contrivances, will avail any thing; and were there no one to rise against them, they would yet fall of themselves. It afterwards follows —

Nahum 3:13

13. Behold, thy people in the midst of thee are women: the gates of thy land shall be set wide open unto thine enemies: the fire shall devour thy bars.

13. Ecce populus tuus mulieres in medio tui; inimicis tuis aperiendo aperientur portae terrae tuae; vorabit ignis vectes tuos.