戍 originally pictured a person carrying a halberd — a soldier on duty. From the Qin and Han onward,
戍边 carried two senses simultaneously: the proud one (loyal soldiers defending the realm — Tang frontier poetry by
王昌龄,
高适,
岑参 is built on this) and the punitive one (criminals and disgraced officials exiled to walk the walls — see Lin Zexu (
林则徐) sent to Yili after the Opium War).