Alongside the French occupation of the left bank of the Rhine, in the course of 1794 secularization also marched in.
After the appointment of a French military administration, this immediately took control of all the regional rights of the hitherto existing ecclesiastical states, like jurisdiction and feudal taxes, such as Church tithes. Thus ended the state of what had been sovereign territories - in practice long before the peace treaty of Lunéville. This series of events is described as the secularization of estates.
Exactly the same fate befell the three Archbishoprics of Cologne, Mainz and Trier, as well as the free cities of the Holy Roman Empire on the left bank of the Rhine, such as Cologne, or secular, self-governing domains under the Kaiser, like Dyck, Prussian areas like Kleve, or Bavarian regions like the Rhineland Palatinate, or even the Austrian-owned Netherlands.
Furthermore, the military administration involved the ecclesiastical institutions to a considerable extent in contributions, requisitioning wood, cattle and food. Numerous churches and monasteries served for a while as accommodation for soldiers, or as stables for horses and storage magazines.
In the framework of the secularization of property, in 1796 ecclesiastical ownership and the right of disposal of the clergy were withdrawn, then finally confiscated in 1798. At the beginning of 1798 France completely abolished feudal rights, insofar as these applied to persons, and the feudal charges, which were based on land ownership. An exception was made for those contributions and services which could be clearly identified, proven by the original documents, as having a non-feudal provenance, which was only successful in rare cases. Because the contributions hitherto collected, for instance the tithes, at that time then flowed into the coffers of the French Treasury, these measures affected the original owners less than the French State.
However, the secular French legislation could not be fully applied until the recognition of annexation in national law after the peace treaty of Lunéville on 9th February 1801, which led to the conclusive dispossession of ecclesiastical goods and their sale.
Ecclesiastical institutes were dissolved by order of the Consul from the 9th June 1802. This move had already been given the blessing of Pope Pius VII in canon law, in the concordat of 15th July 1801. The members of the ecclesiastical institutes - convents, monasteries and seminaries – had to leave the buildings. They were given travelling expenses and ordered to leave French territory if they originated from the area on the right side of the Rhine, or received a pension if they came from the left side of the Rhine. However, the pensions were not particularly high and at first were only paid after some delays. Almost all the male clerics were able to find posts as parish priests, or as curates. On the other hand, the female clergy was obliged to withdraw into private life. Most of the ecclesiastical ladies found accommodation with members of their families. In parallel actions, the goods of hostile secular rulers were also expropriated, as were those of emigrants, whereby this series of events also counted as the rights of annexation.
In total, between 1803 and 1813 on the left bank of the Rhine over 16,500 secularized or annexed properties of various sizes and compositions were auctioned off. In addition, there were numerous other properties which had been combined in state forests, endowments, or extraordinary crown domains. A large part of these was not disposed of until Prussian times – with the exception of the large woodlands.
The effects of secularization were diverse. The dispossession of the clergy and their status as quasi-public servants on state pay has remained until today. The disappearance of the (wealthy) monasteries also meant one less source of credit, which had lent at moderate rates of interest, sometimes even for large sums, which in turn had a corresponding effect on the economy. Moreover, there was a massive restructuring of ownership. Many former tenant farmers were able to acquire their leased land as freehold property. However, groups also formed of large buyers, speculators and real estate dealers. Incidentally, around 200 years ago the Rhinelander showed no inhibitions about buying former church land. Although the farmers had been freed from feudal charges, they still had to reckon with the disadvantages of remaining tenants. In years of bad harvests the rents were no longer reduced by the new secular owners, as the ecclesiastical proprietors had often used to do. With the proceeds of confiscations, as well as later returns from auctions, France was able to settle its debts and Napoleon was in a position to finance his wars.
The French practice of secularization also affected the Holy Roman Empire of the German Nation. On the right side of the Rhine the clergy was also secularized, according to the main conclusion of the imperial deputation in 1803, and many small states bordering directly on the Empire were annexed. In total 112 estates of the Empire were abolished. From this mass the larger German states received compensation for their losses on the left side of the Rhine.