Regent of Saxony
His older brother, the Elector Frederick Christian, died on 17 December 1763 after a reign of only 74 days. Franz Xavier took over the regency of the Electorate together with his sister-in-law, the Dowager Electress Maria Antonia of Bavaria, on behalf of his infant nephew, the new Elector Frederick Augustus III. As co-regent, Franz Xavier continued the rationalistic reforms of his brother.
In October 1765, Franz Xavier performed in the name of the young Elector a formal renunciation of the Polish Crown in favor of Stanislaus Poniatowski, as was required by the treaty signed between Prussia and Russia on 11 April 1764. This was done against the wishes of the boy's mother, the Dowager Electress Maria Antonia. During the regency, Franz Xavier attempted to introduce a plan of army reform based upon the Prussian model of Frederick the Great. This brought him into conflict with the estates of the country, who violently refused to implement his proposal because of the high expense associated with his reorganization plan.
According to the regulations imposed by the Golden Bull of 1356, the regency of an underage Elector ended when he reached his eighteenth birthday. As a result, in 1768, the Elector Frederick Augustus III was formally proclaimed an adult, and Franz Xavier ended his functions as the regent of the Electorate of Saxony.
Read more about this topic: Prince Francis Xavier Of Saxony, Life