Complex sentence: Gorchakov took part as a general officer in the Italian and Swiss operations of 1799 together with general Rimsky-Korsakov, and in the war against Napoleon in Poland in 1806--1807 (Battle of Heilsberg).
Split into simpler sentences: Gorchakov took part as a general officer in the Italian and Swiss operations of 1799 together with general Rimsky-Korsakov. He then served in the next war against Napoleon in Poland in 1806--1807 (Battle of Heilsberg).