Complex sentence: Most of the imperial cities, imperial abbies, and ecclesiastical states and cities were mediatized or secularized in 1803; with the final dissolution of the Holy Roman Empire in 1806, many of the tiny principalities were annexed by larger neighbors.
Split into simpler sentences: Most of the imperial cities, imperial abbies, and ecclesiastical states and cities were mediatized or secularized in 1803. With the final dissolution of the Holy Roman Empire in 1806, many of the tiny principalities were annexed by larger neighbors.