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In politics and law, mediatisation ( //) is the loss of immediacy, the status of persons not subject to local lords but only to a higher authority directly, such as the Holy Roman Emperor. In a feudal context, it is the introduction of an intervening level of authority between a lord and his vassal so that the former is no longer the immediate lord of the latter, but rather his lordship is mediated by another.
Although the process had been going on since the Middle Ages, the term "mediatisation" was originally applied to the reorganisation of the German states during the early 19th century. In this case, many states that were immediate vassals of the Holy Roman Emperor became instead vassals of other immediate states so that the total number of states immediately subject to the emperor decreased.
Holy Roman Empire
Between 1803 and 1806, the final years of the Holy Roman Empire, the vast majority of the states of the Holy Roman Empire were mediatised. These states lost their imperial immediacy (Reichsunmittelbarkeit) and became part of other states. The number of states was reduced from about three hundred to about thirty. Mediatisation went along with secularisation: the abolition of most of the ecclesiastical states.
The legal basis for mediatisation was the Reichsdeputationshauptschluss of 1803, which had become necessary under pressure from France. The Treaty of the Confederation of the Rhine of 1806 continued the process of mediatisation. The constitution of the German Confederation of 1815 confirmed the mediatisation, but preserved certain rights for the mediatised princes within their former realms, now ranked as state countries, such as first instance jurisdiction, supervision of religion and foundations.
Mediatised sovereign houses rank higher than other houses of nominally equal (or higher) rank, but who never ruled a state. This division had great social significance, as mediatised princes were considered equal to royals for marriage purposes; in essence they were regarded as royalty. However, there were two types of mediatised families; old and new. Old were those who have for centuries ruled immediate imperial territories. New families were those who obtained immediate status after the end of the Middle Ages, mostly as a reward for service and loyalty to the reigning Emperor. Most of these families came from hereditary Habsburg lands and south-western Germany; originally they were mediate nobles, upgraded to immediate status. After the mediatisation, these families were officially regarded as equals to royalty; however, the reigning houses often, but not always declined to treat them as such. Emperor Franz Joseph, for example, forbade his nephew’s son, future Charles I of Austria, even to consider a possible match with a Hohenlohe princess even though the Hohenlohes were an old family who reigned for centuries prior to the mediatisation, and King Frederick William III of Prussia had to marry morganatically the Countess Auguste von Harrach even though she came from a mediatised family. Thus in theory, if a scion from the most obscure mediatised family (say the child of an impoverished mediatised count) married an emperor or a king, their alliance was considered equal, not morganatic, and their children had dynastic rights. In practice, however, this never happened. The authoritative guide to the royal and noble houses of Europe, the Almanach de Gotha, has been, since the late 19th century, divided into three sections: sovereign houses, mediatised houses, and noble houses.