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
By a
great victory, after which Hiero was proclaimed king of the Siceliots
(484), he succeeded in shutting up the Mamertines within their city,
and after the siege had lasted some years, they found themselves
reduced to extremity and unable to hold the city longer against Hiero
on their own resources. It is evident that a surrender on stipulated
conditions was impossible, and that the axe of the executioner, which
had fallen upon the Campanians of Rhegium at Rome, as certainly
awaited those of Messana at Syracuse.
Their only means of safety lay
in delivering up the city either to the Carthaginians or to the
Romans, both of whom could not but be so strongly set upon acquiring
that important place as to overlook all other scruples. Whether it
would be more advantageous to surrender it to the masters of Africa
or to the masters of Italy, was doubtful; after long hesitation the
majority of the Campanian burgesses at length resolved to offer
the possession of their sea-commanding fortress to the Romans.