Complex sentence: His father, an officer in the French army, perished in the Russian campaign of 1812; the family then moved to Liege, where the eldest son, Firmin, held a professorship.
Split into simpler sentences: His father, an officer in the French army, perished in the Russian campaign of 1812. The family then moved to the Belgian city of Liege, where the eldest son, Firmin, held a professorship.