During the Seven Years' War (1756–1763) he rendered signal services to his country as intermediary between the opposing camps, and through his influence warded off many a calamity from the city and principality of Münster.
[1] After the death of Clemens August, Elector of Cologne and Prince-Bishop of Münster, on 6 February 1761, it was chiefly through the influence of Fürstenberg that Maximilian Friedrich von Königsegg-Rothenfels, who had succeeded Clemens August at Cologne (6 April 1761), was also elected Prince-Bishop of Münster in September, 1762.
No better man could have been found to manage the temporal and spiritual affairs of the Prince-Bishopric of Münster which had suffered severely during the Seven Years' War.
To restore prosperity to the people he improved agricultural conditions by dividing the land into marks, draining marshes and reclaiming much soil which hitherto had lain idle or in pasturage.
In order to liquidate the public debt he placed a duty on such imported goods as could be easily dispensed with, and for a space of six years levied a moderate capitation tax from which the privileged estates were not exempted.
He improved the military and the sanitary system, the former by founding a military academy at Münster and by introducing something similar to the "Landwehr" or militia, the latter by founding a college of medicine (1773) and inducing its director, the learned Christopher Ludwig Hoffmann, to draw up a code of medicinal regulations which was justly admired through Germany as a model of its kind.
[1] In 1780 Fürstenberg was dismissed from his ministerial office because he had campaigned for the introduction of a standing army, had plans to excavate a canal in the direction of the Rhine, and had encountered energetic resistance.
The baron, however, remained vicar general until 1807 and kept the supervision over the school system, during whose reform his friend Bernhard Heinrich Overberg supported him above all.