suzerain state
A state that exercises political control over a dependent state, especially in historical contexts such as tributary systems or colonial relationships.
The Qing dynasty claimed suzerainty over neighboring countries.
宗主国と属国の関係は、歴史的に様々な形で存在した。
Relationships between suzerain states and vassal states have existed in various forms throughout history.
保護国 is a protectorate, a state under the protection of another, often with more autonomy than a vassal state under a 宗主国.
Compound of 宗主 (suzerain) and 国 (country). The term is used in historical and political contexts to describe a dominant state in a suzerain–vassal relationship.