《资治通鉴·汉纪·汉纪十八》
如果发兵出击，即使不能灭亡先零，但能禁绝羌人小规模的侵扰活动，则可以出兵。
诚令兵出，虽不能灭先零，但能令虏绝不为小寇，则出兵可也。
If you send troops into action, and even if you cannot exterminate the Xianling, if you can stop the small-scale raiding activities of the Qiang, then you can send troops.