A tribute (from Latin tributum, contribution) is wealth, often in kind, that one party gives to another as a sign of respect or, as was often the case in historical contexts, of submission or allegiance. Various ancient states exacted tribute from the rulers of land which the state conquered or otherwise threatened to conquer. In case of alliances, lesser parties may pay tribute to more powerful parties as a sign of allegiance and often in order to finance projects that benefited both parties. To be called "tribute" a recognition by the payer of political submission to the payee is normally required; the large sums, essentially protection money, paid by the later Roman and Byzantine Empires to barbarian peoples to prevent them attacking imperial territory, would not usually be termed "tribute" as the Empire accepted no inferior political position. Payments by a superior political entity to an inferior one, made for various purposes, are described by terms including "subsidy".The ancient Persian Achaemenid Empire is an example of an ancient tribute empire; one that made relatively few demands on its non-Persian subjects other than the regular payment of tribute, which might be gold, luxury goods, animals, soldiers or slaves. However failure to keep up the payments had dire consequences. The reliefs at Persepolis show processions of figures bearing varied types of tribute.The medieval Mongol rulers of Russia likewise only expected tribute from the Russian states, which continued to govern themselves. Athens received tribute from the other cities of the Delian League. The empires of Assyria, Babylon, Carthage and Rome exacted tribute from their provinces and subject kingdoms. Ancient China received tribute from various states such as Japan, Korea, Vietnam, Cambodia, Borneo, Indonesia and Central Asia. The Aztec Empire is another example. The Roman republic exacted tribute in the form of payments equivalent to proportional property taxes, for the purpose of waging war.Tribute empires contrast with those like the Roman Empire, which more closely controlled and garrisoned subject territories. A tributary state is one that preserves its political position and such independence as it has only by paying tribute.