noun
western army
General term for a western army in a civil war or conflict. Can refer to any historical or fictional western force.
内戦では西軍が一時的に首都を占領した。
In the civil war, the western army temporarily occupied the capital.
noun
Western Army (Sekigahara)
Specifically refers to the Western Army led by Ishida Mitsunari at the Battle of Sekigahara in 1600. A historical proper noun.
関ヶ原の戦いで西軍は東軍に敗れた。
At the Battle of Sekigahara, the Western Army was defeated by the Eastern Army.