A vassal state is secondary to a dominant state. It is subordinate in nature. In this case, the term vassal refers to the ruler and not the state itself. The vassal has authority on the subordinate state in many aspects: military, political and economic.
The relationship between the ruler state and the vassal state is mainly anchored on military affairs. The vassal state provides military assistance to the dominant state whenever requested to do so. On the other hand, the dominant state offers protection and security to the vassal state while performing several other functions that improve their welfare. Where more military support is required, the vassal state provides military power to the overlord at no cost. This creates an interdependence where the vassal state ranks secondary.
Vassal States vs Tributary States
The difference between a vassal state and a tributary state is that a tributary state pays tribute to the dominant state (Suzerain) in the form of taxes and tariff exemptions while a vassal state is simply dominated on military affairs. Both are similar in that they are secondary to a more powerful nation or state. However, of the two, a vassal state has more independent power than a tributary state.
Characteristics of Vassal States
Although similar in many ways, a vassal state has many characteristics that distinguish it from a tributary state, protectorate, or associated state.
Examples of Vassal States
Ancient vassal states included Wallachia, Crimean Khanate, and Moldavia who were vassals of the Ottoman Empire. The states of Chu and Qi were vassals to the Zhou Dynasty in ancient China. The legendary city of Troy (3000 BCE to 500 CE) was a vassal state of the Hittite empire.