His mission is to set up the new branch office.
兵士たちは困難な任務を遂行した。
The soldiers carried out a difficult mission.
He fulfilled his duty.
The unit carried out the assigned mission.
His boss gave him a new mission.
She was assigned to take on that duty.
The soldier bears a heavy duty.
He abandoned his duty and fled.
任務 is a more formal word for an officially assigned mission or task, whereas 役目 can describe any expected duty, formal or informal.
任務 is a formal term for a duty or assigned task (often military or professional), whereas クエスト is casual gaming slang for a quest.
任務 refers to a specific task or mission one is assigned to carry out, whereas 責任 refers more broadly to the accountability or burden behind fulfilling any duty.
任務 is a concrete task or mission assigned to someone, while 責務 stresses the sense of duty attached to a position rather than a specific task.
任務 is a neutral, task-oriented word for an assigned duty or mission, whereas 重責 specifically highlights how serious or heavy that duty is.
military mission