gǔ / dài / jūn / duì / cháng / cháng / zài / biān / jìng / tún / shù / yǐ / fáng / dí / jūn / rù / qīn

古代军队常常在边境屯戍，以防敌军入侵。

Ancient armies often garrisoned the border to prevent enemy invasions.