 Complete the following phrase:  Wilhelm Christoforovich Derfelden ; 1737  20 September 1819 was an Imperial Russian General of the Cavalry from a family of Baltic Germans. He fought in the Russo-Turkish War of 17681774, Russo-Turkish War of 17871792, PolishRussian War of 1792, and Kościuszko Uprising of 1794. In the latter conflict he led troops in the battles of Chełm and 