Fetching details from the dictionary...
to depart (for military service); to go (into battle)
若者たちは戦場へ征く決意を固めた。
The young men resolved to go to the battlefield.
父は二十歳のとき戦地に征いた。
My father went to the front when he was twenty.
多くの兵士が戦場へ征っている。
Many soldiers have departed for the battlefield.