Vassal state

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.

Ancient China
From the time of the Zhou Dynasty (1046–770 BCE) until the Han Dynasty (206 BCE–220 CE), a varying number of vassal states existed in Ancient China. These ranged in size from small city states to vassals which controlled large swathes of territory such as the States of Chu and Qi. One of these vassal states would go on to conquer China and unite the country under the first emperor Qin Shi Huang.

People's Republic of China
Between 1949 and 1950 Tibet was invaded by Forces from the People's Republic of China (PRC) forcing the then Tibetan government into exile. Until the late 1950s Chinese writers became used to "describing Tibet's place in the world of imperial China as that of a subordinate vassal state."

Ottoman Empire
The Ottoman Empire (1299–1923 CE) controlled a number of tributary or vassal states in the peripheral areas of its territory. Vassalage took a number of different forms with some states permitted to elect their own leaders. Other states paid tribute for their lands. During the 1700s the Ottoman Empire controlled many states such as the Berber people and Crimean Khanate.

Troy under the Hittites
Troy was a vassal state of the Hittites, along with other Arzawa lands.