assistant inspector
A specific rank in the Japanese police force, below inspector (警部) and above sergeant (巡査部長).
He was promoted to assistant inspector.
Assistant inspectors often take command at the scene.
He was promoted to assistant inspector after three years.
巡査部長 is the rank directly below 警部補, and the two are easily confused when listing police hierarchy.
Compound of 警部 (inspector) and 補 (assistant, supplementary). The term is a modern bureaucratic coinage for the police rank system.