Natural son of Leopold I of Anhalt-Dessau (1676-1747) and Sophie Elonore Söldener (1710-1779).
Von Berenhorst was adjutant to Prince Heinrich of Prussia from 1757 to 1760, and in 1760 even to the Prussian King Frederick II (the Great). Having attained the rank of Major, he was dismissed from Prussian service in 1761. In the next three decades, he held various positions at the court of Anhalt-Dessau, including those of Chamber President and Marshall to the Court, before in 1790 he retired and devoted the rest of his life to research and writing. Today he is best remembered for his influential book on military history Betrachtungen über die Kriegskunst (1796-1799) (EN: Observations on the Art of War, Its Progress, Its Contradictions, and Its Reliability)
On September 24, 1764, Boswell noted that Berenhorst had been very kind to him on that day, at the Court of Anhalt-Dessau. On the 25th, Berenhorst introduced Boswell to Prince Dietrich of Anhalt-Dessau.
When Boswell left Dessau on October 1, he noted his intention to keep up a correspondence with Neitschütz and Berenhorst, but, as was the case with most of the friends he made during his tour of Germany, he apparently never did.
Some of Berenhorst writings, as well as a few short biographies of him, are often available via the AbeBooks used books search engine.