He participated in the Russo-Turkish campaign in 1788-89 and was transferred to the Ostrogozh Light Cavalry Regiment in 1790. During the campaign in Poland in 1794, he distinguished himself by capturing General Tomasz Wawrzecki and his officers, and was promoted to major. In October 1799, he was transferred to the Life Guard Hussar Regiment and promoted to colonel. On 23 October 1806, Duka was appointed "chef" of the Little Russia Cuirassier Regiment. He took part in the 1807 Campaign and distinguished himself at Eylau, being awarded the Order of St. George (3rd Class) and a Golden Weapon "For Bravery". He was promoted to major general on 6 June 1807.