Complex sentence: By the late 18th century, much of the Cossack officer class in Ukraine was incorporated into the Imperial Russian nobility (Dvoryanstvo), but many of the rank and file Cossacks, including a substantial portion of the old Zaporozhians, were reduced to peasant status.
Split into simpler sentences: By the late 18th century, the Cossack officer class in Ukraine was incorporated into the Imperial Russian nobility (Dvoryanstvo). The rank and file Cossacks however, including a substantial portion of the old Zaporozhians, were reduced to peasant status.