What is a ruler or state that pays tribute, or a stated sum, to a conquering power, for the purpose of securing peace and protection, or as an acknowledgment of submission, or for the purchase of security called?

tributary — A ruler or state that pays tribute, or a stated sum, to a conquering power, for the purpose of securing peace and protection, or as an acknowledgment of submission, or for the purchase of security. (Webster's 1913.)

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