an army
the whole army; the entire force
《sports》first team; first-string players
the cool kids; the popular kids
敵の一軍が国境を越えてきた。
An enemy army crossed the border.
大将は一軍を率いて出陣した。
The general led an army into battle.
織田軍は一軍を三つの方向から城に向けて進軍させた。
Oda's forces marched an army toward the castle from three directions.