Complex sentence: Later, imperial orders such as the Carolingians, the Ottonians, and Hohenstaufens also imposed their overlordship in Italy, but their successes were as transitory as Justinian's success, and a unified Italian state remained a dream until the nineteenth century.
Split into simpler sentences: Later, Imperial orders such as the Carolingians, the Ottonians, and Hohenstaufens also managed to impose their overlordship in Italy. But their successes were as transitory as Justinian's success, and a unified Italian state remained a dream until the nineteenth century.