Complex sentence: After the French invasion of Piedmont followed to Victor Amadeus II of Savoy's refusal to cease the fortress of Turin, the French army, led by Nicolas Catinat, after the conquest of the strongholds of Pinerolo and Avigliana, laid siege to the Cuneo fortress.
Split into simpler sentences: After the French invasion of Piedmont followed by Victor Amadeus II of Savoy's refusal to surrender the fortress of Turin, the French army attacked. Led by Nicolas Catinat, the French conquered the strongholds of Pinerolo and Avigliana, then laid siege to the Cuneo fortress.