[1] Marcellus learnt that some leaders in the city had been conspiring with Hannibal, and he discovered that should he make any sortie from the town or draw up for battle outside, they planned on plundering the baggage and closing the gates behind him.

[1] He took action to protect himself from a revolt, pulled his troops from the walls, and secretly organized them behind the gates.

When nothing happened, Hannibal concluded that Marcellus had uncovered his plan and would not dare attempt a sortie with the threat of betrayal.

When they did this, Marcellus sprang his trap and ordered his forces to charge out of the gates and personally lead the centre.

The victory, while not decisive enough to end Hannibal's fighting potential, was a boost to Roman morale.