first reserve service; reserve duty
Refers to the status of being in the first reserve of a military force, typically after active duty. Common in contexts discussing military organization and personnel categories.
He was transferred to the first reserve.
Reserve officers participated in the training.
Active duty, as opposed to reserve status.
Compound of 予備 (reserve, spare) and 役 (duty, service). The term is a straightforward Sino-Japanese coinage for military reserve service.