The Captain of the Guard is the commanding position of a military

Military

A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

 security force. The position of Captain of the Guard is not or no longer associated with the rank of Captain. The Guard is commonly associated with bodyguard

Bodyguard

A bodyguard is a type of security operative or government agent who protects a person—usually a famous, wealthy, or politically important figure—from assault, kidnapping, assassination, stalking, loss of confidential information, terrorist attack or other threats.Most important public figures such...

 duty for royalty

Monarchy

A monarchy is a form of government in which the office of head of state is usually held until death or abdication and is often hereditary and includes a royal house. In some cases, the monarch is elected...

 or head of state

Head of State

A head of state is the individual that serves as the chief public representative of a monarchy, republic, federation, commonwealth or other kind of state. His or her role generally includes legitimizing the state and exercising the political powers, functions, and duties granted to the head of...

, but the Guard can refer to the military security force of a city

City

A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...

 or region such as a province

Province

A province is a territorial unit, almost always an administrative division, within a country or state.-Etymology:The English word "province" is attested since about 1330 and derives from the 13th-century Old French "province," which itself comes from the Latin word "provincia," which referred to...

, state, or territory.