noun
eastern army
General term for an army positioned in or coming from the east, especially in a civil war context.
内戦では東軍と西軍に分かれて戦った。
In the civil war, they fought divided into the eastern army and the western army.
noun
Eastern Army (Sekigahara)
Historical term specifically referring to the Eastern Army led by Tokugawa Ieyasu at the Battle of Sekigahara in 1600.
関ヶ原の戦いでは、東軍が西軍を破った。
At the Battle of Sekigahara, the Eastern Army defeated the Western Army.