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war; campaign; battle
「役」 has another reading with different meanings.
映画で主役を演じることになった。
I played the lead role in the movie.
彼女は悪役を演じるのがうまい。
She is good at playing villains.
関ヶ原の役は日本の歴史で重要な戦いだ。
The Battle of Sekigahara was an important war in Japanese history.