noun
reserve officers
Military term for officers in the reserve forces, as opposed to active-duty officers.
彼は予備将校として訓練を受けた。
He received training as a reserve officer.
予備役 refers to the reserve duty or reserve service itself, while 予備将校 specifically denotes the officers in that reserve.
Compound of 予備 (reserve, spare) and 将校 (commissioned officer).