Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
The patriotic party had the
ascendency among the citizens; it was resolved to allow the opposition
to negotiate for peace, and meanwhile to prepare for a last and
decisive effort. Orders were sent to Mago and Hannibal to return with
all speed to Africa. Mago, who for three years (549-551) had been
labouring to bring about a coalition in Northern Italy against Rome,
had just at this time in the territory of the Insubres (about Milan)
been defeated by the far superior double army of the Romans.
The
Roman cavalry had been brought to give way, and the infantry had been
thrown into confusion; victory seemed on the point of declaring for
the Carthaginians, when a bold attack by a Roman troop on the enemy's
elephants, and above all a serious wound received by their beloved and
able commander, turned the fortune of the battle. The Phoenician army
was obliged to retreat to the Ligurian coast, where it received and
obeyed the order to embark; but Mago died of his wound on the voyage.