The nephew of the Wallachian Spatharios Pârvu Cantacuzino, who was killed in a skirmish with the Turks in 1769, Radukan Cantacuzino joined the volunteers' detachment of Count Rumyantsev's army, acting against the Turks, and participated in the Battle of Kagul. Later he was admitted to the Russian service together with the regiment, which he formed from the natives of Wallachia.