Explanation: During the Second Punic War, the great Carthaginian ('Punic') general Hannibal Barca managed to successfully lead an army - and accompanying war elephants - across the Alps - both feats considered impossible or near-to-it due to the poor state of trails (and weather) in the Alps and the large number of hostile barbarian tribes.

The Romans were... quite surprised by this, and had difficulty responding to the unexpected attack on the Italian heartland, when they presumed that the war would happen mostly in Spain or at sea.

Surprise elephants in your heartland are going to throw your plans for the day into chaos, no matter what.

the great Carthaginian (‘Punic’) general

The word 'punic' comes from 'puny', by the way. Not very great indeed.