towns of Lüneburg and Brunswick remained in the overall possession of the House of Welf until 1512 and 1671 respectively. In 1571 the Amt of Calvörde became an exclave of the Duchy. The various parts of the duchy were further divided and re-united over the centuries, all of them being ruled by the Welf or Guelph dynasty, who maintained close relations with one another—not infrequently by marrying cousins—a practice far more common than is the case today, even among the peasantry of the Holy Roman Empire, for the salic inheritance laws in effect, encouraged the practice of retaining control of lands and benefits. The seats of power moved in the meantime from Brunswick and Lüneburg to Celle and Wolfenbüttel as the towns asserted their independence. History of the subordinate principalities The subsequent history of the dukedom and its subordinate principalities was characterised by numerous divisions and reunifications. The subordinate states that were repeatedly created, and which had the legal status of principalities, were generally named after the residence of their rulers. The estates of the different dynastic lines could be inherited by a side line when a particular family died out. For example, over the course of the centuries there were the Old, Middle and New Houses (or Lines) of Brunswick, and the Old, Middle and New Houses of Lüneburg. The number of simultaneously reigning dynastic lines varied from two to five. Principality of Brunswick-Wolfenbüttel In 1269 the Principality of Brunswick was formed following the first division of the Duchy of Brunswick-Lüneburg. In 1432, as a result of increasing tensions with the townsfolk of Brunswick, the Brunswick Line moved their Residence to Wolfenbüttel, into the water castle, which was expanded into a Schloss, whilst the town was developed into a royal seat. The name Wolfenbüttel was given to this principality. From 1546 Wolfenbüttel became the residence of the senior prince of Brunswick-Lüneburg, Henry, Duke of Brunswick-Dannenberg. With sole rights to the duchy Brunswick-Lüneburg, he provided a conditional sub-lease of the principality of Lüneburg to the princes of Calenburg with the conditions of payment to the Wolfenbüttel heirs (Chief of the House), together with the guarantee that only his descendants would inherit this senior principality of Wolfenbüttel. Not until 1753/1754 was the Residence moved back to Brunswick, into the newly built Brunswick Palace. In 1814 the principality became the Duchy of Brunswick, with its own subordinate principalities that are all apart