A vassal state is any state that is subordinate to another. The vassal in these cases is the ruler, rather than the state itself. Being a vassal most commonly implies providing military assistance to the dominant state when requested to do so; it sometimes implies paying tribute, but a state which does so is better described as a tributary state. In simpler terms the vassal state would have to provide military power to the dominant state. Today, more common terms are puppet state, protectorate or associated state.