Rising to the throne at the age of eighteen in 222 BC , his early campaigns against the Ptolemaic Kingdom were unsuccessful .
In the following years Antiochus gained several military victories and substantially expanded the empire 's territory .
Rising to the throne at the age of eighteen in 222 BC , his early campaigns against the Ptolemaic Kingdom were unsuccessful , but in the following years Antiochus gained several military victories and substantially expanded the empire 's territory .