His light-armed troops and horsemen were drawn up in concealment on either side.
The Roman column advanced (May, 217), without hesitation, to the unoccupied pass, the thick morning mist completely concealing the position of the enemy.

As the Roman vanguard approached the hill, Hannibal gave the signal for attack.

The cavalry closed up the entrance to the pass, and at the same time the mist rolled away, revealing the Carthaginian arms on the right and left.

It was not a battle, but a mere rout.

The main body of the Romans was cut to pieces, with scarcely any resistance, and the Consul himself was killed.