 Complete the following phrase:  By the 18th century, Cossack hosts in the Russian Empire occupied effective buffer zones on its borders. The expansionist ambitions of the Empire relied on ensuring Cossack loyalty, which caused tension given their traditional exercise of freedom, democracy, self-rule, and independence. Cossacks such as Stenka Razin, Kondraty Bulavin, Ivan Mazepa and Yemelyan Pugachev led major anti-imperial wars and revolutions in the Empire in order to abolish slavery and harsh bureaucracy, and to maintain independence. The empire responded with executions and tortures, the destruction of the western part of the Don Cossack Host during the Bulavin Rebellion in 17071708, the destruction of Baturyn after Mazepas rebellion in 1708, and the formal dissolution of the Lower Dnieper Zaporozhian Host after 