Jamieson, Fausset and Brown on Nahum 3:15

15. There--in the very scene of thy great preparations for defense; and where thou now art so secure.

fire--even as at the former destruction; Sardanapalus (Pul?) perished with all his household in the conflagration of his palace, having in despair set it on fire, the traces of which are still remaining.

cankerworm--"the licking locust" [Henderson].

make thyself many as the locusts--"the swarming locusts" [Henderson]; that is, however "many" be thy forces, like those of "the swarming locusts," or the "licking locusts," yet the foe shall consume thee as the "licking locust" licks up all before it.