Lentulus initially refused Frederick's request, but left the Austrian army to go to Bern. After the peace settlement of 1745, Prince
Leopold I, Prince of Anhalt-Dessau intervened with Lentulus and convinced him to enter the Prussian army. Lentulus entered the Prussian army in 1746 as a cavalry officer with a
major's commission. Frederick appointed him as a wing adjutant and revised his officer's patent (commission) to the date of the surrender of Prague. In April 1758, he took part in the
Siege of Schweidnitz with seven cuirassier regiments and then moved with Frederick's army to
Moravia. In the battles of
Zorndorf and
Hochkirch, he again led by example. In 1759 he served in Silesia. In 1760, he fought at the head of two dragoon regiments in the
Battle of Liegnitz, and commanded the post roads in Silesia in the following winter. The end of his service in this war was, for Lentulus, the
Battle of Reichenbach on 16 August 1762. Lentulus gave up the office in 1779. As during his entire career in Prussia, Lentulus often belonged to the king's closest circles, especially during the years after the war, where he was valued because of his education and intelligence. As early as 1752 Lentulus was present at the wedding of the brother of King,
Henry, with the Hessian
Princess Wilhelmine. In 1769, Lentulus was present in
Neisse at the meeting of Frederick II with Austrian
Emperor Joseph II. Following the
First Partition of Poland, Frederick sent him to
East Prussia in 1773 to take possession of the newly-acquired province and to establish Prussian rule. In 1778–79, Lentulus took part in the service of Prince Henry during the
War of Bavarian Succession, but retired because of his old age. Upon his retirement, Lentulus returned to Bern, where he headed the military system. On the recommendation of Lentulus, the city and the Republic of Bern had already formed the first three
Jäger companies in 1768 from good marksmen of the upper regiments. ==Memorials and honors==