Protectorate (imperial China)
Protectorate, also known as Duhu Fu (Chinese: 都護府), was a type of administrative division of the Chinese Empire, especially during the Han and Tang dynasties, established in frontier regions. During the Han and Tang dynasties, a protectorate was the highest government agency in frontier areas and was directly responsible to the imperial court.
Source: Wikipedia — Protectorate (imperial China) (CC BY-SA 4.0)