Complex sentence: At that time he saw the creation of the Duchy of Warsaw by the Emperor as a stepping stone to eventual full independence for the Commonwealth, and dedicated his only opera, "Zelis et Valcour", to Napoleon.
Split into simpler sentences: At that time he saw the creation of the Duchy of Warsaw by the Emperor as a stepping stone to eventual full independence of the Commonwealth. He dedicated his only opera, "Zelis et Valcour", to Napoleon.