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 great victory, which he gained in 556 over the Egyptian general
Scopas at Mount Panium near the sources of the Jordan, not only gave
him complete possession of that region as far as the frontier of Egypt
proper, but so alarmed the Egyptian guardians of the young king that,
to prevent Antiochus from invading Egypt, they submitted to a peace
and sealed it by the betrothal of their ward to Cleopatra the daughter
of Antiochus.
When he had thus achieved his first object, he
proceeded in the following year, that of the battle of Cynoscephalae,
with a strong fleet of 100 decked and 100 open vessels to Asia Minor,
to take possession of the districts that formerly belonged to Egypt on
the south and west coasts of Asia Minor--probably the Egyptian
government had ceded these districts, which were -de facto- in the
hands of Philip, to Antiochus under the peace, and had renounced all
their foreign possessions in his favour--and to recover the Greeks of
Asia Minor generally for his empire. At the same time a strong Syrian
land-army assembled in Sardes.