Vassal State

This is exact opposite of a Suzerainty.

A vassal state is the subservient/smaller state in a mutually obligatory political relationship. When a smaller, weaker nation cozies up to a larger, more powerful nation, it’s termed a vassal state, much like vassals were subjects of a kingdom’s power and protection in medieval times.

“Vassal” is literally Old French for “subject, subordinate, servant.”