An Imperial Russian Army officer during the Seven Years' War, Chernyshev retired in 1764, and would be ultimately promoted to general field marshal by Catherine II.

At her appointment, Chernyshev led the College of War from 1764 to 1774, served as her governor-general of the Pskov and Mogilev Governorates, and was the mayor of Moscow until his death.

[3] When he returned to Saint Petersburg six years later, Chernyshev began actively courting the then-grand duchess: flattering Catherine, sending love letters, and finding occasion to recreate with the royal.

For his leadership in the 1758 Battle of Zorndorf and the 1760 occupation of Berlin—capital of the Kingdom of Prussia, Chernyshev was awarded the Order of Saint Alexander Nevsky.

[1] In early 1762, then-General Chernyshev commanded a Russian corps of 16,000 infantry in Silesia that was attached to the Austrian army, fighting the Prussian kingdom.

"[2] In 1742, Kapitan Chernyshev was sent to the Holy Roman Empire city of Vienna, where he worked under the Russian ambassador there, Ludovic Lanczynski.

[1] He commissioned Matvey Kazakov, and had a luxury home built on Tverskaya Street that would house Muscovite mayors into the 20th century.