Complex sentence: Catherine II of Russia officially abolished the institute of Hetman in 1764 and in 1764-1781 Cossack Hetmanate was incorporated as the Little Russia Governorate headed by Pyotr Rumyantsev.
Split into simpler sentences: Catherine II of Russia officially abolished the institute of Hetman in 1764. In 1764-1781 Cossack Hetmanate was incorporated as the Little Russia Governorate headed by Pyotr Rumyantsev.