royal guard; imperial guard; monarch's personal guard
Refers to guards or troops assigned to protect a monarch or ruler directly. In modern usage it is especially common as the first element of compounds such as 親衛隊.
The king's royal guard was guarding the palace gate.
The emperor chose trusted soldiers as his personal guards.
Sino-Japanese compound: 親 suggests closeness or direct relation, and 衛 means guarding or defense. The spelling is conventionally associated with guards who protect a ruler at close range.