Engelhardt was sent in January 1787 to serve on the Caucasus front under Lieutenant General Pavel Potemkin, and they fought the Chechens at the Terek River during the Russian conquest of the Caucasus, then took part in the Russo-Turkish War of 1787-1792. He was at the conquest of the cities of Bender and Kiliya, in a battle with a Turkish fleet on the Danube, and in the storming and capture of Izmail. On March 25, 1791, he was promoted to colonel and awarded the Order of St. George, fourth degree.