Complex sentence: The last duke, Ercole III, was deposed in 1796 by the French and his two duchies became the Cispadane Republic which one year later was merged into the Cisalpine Republic and then into the Napoleonic Kingdom of Italy.
Split into simpler sentences: The last duke, Ercole III, was deposed in 1796 by the French. His two duchies became the Cispadane Republic which one year later was merged into the Cisalpine Republic and then into the Napoleonic Kingdom of Italy.