rear guard; rear guard unit
Military term for the unit or force that protects the rear of a formation, especially during a retreat. Also used metaphorically for the last or trailing element in a group.
See also: 殿軍
The rear guard unit retreated while holding off the enemy's pursuit.
He is running at the back of the pack in the marathon.
Compound of 殿 (しんがり, 'rear guard') and 部隊 (ぶたい, 'unit, force'). The reading しんがり is a specialized military term.