Ukraine was the center of the first Slavic state, Kievan Rus, which during the 10th and 11th centuries was the largest and most powerful state in Europe. Weakened by internecine quarrels and Mongol invasions, Kievan Rus was incorporated into the Grand Duchy of Lithuania and eventually into the Polish-Lithuanian Commonwealth. The cultural and religious legacy of Kievan Rus laid the foundation for Ukrainian nationalism through subsequent centuries. A new Ukrainian state, the Cossack Hetmanate, was established during the mid-17th century after an uprising against the Poles. Despite continuous Muscovite pressure, the Hetmanate managed to remain autonomous for well over 100 years. During the latter part of the 18th century, most Ukrainian ethnographic territory was absorbed by the Russian Empire. Following the collapse of czarist Russia in 1917, Ukraine was able to bring about a short-lived period of independence (1917-20), but was reconquered and forced to endure a brutal Soviet rule that engineered two artificial famines (1921-22 and 1932-33) in which over 8 million died. In World War II, German and Soviet armies were responsible for some 7 to 8 million more deaths. Although final independence for Ukraine was achieved in 1991 with the dissolution of the USSR, democracy remained elusive as the legacy of state control and endemic corruption stalled efforts at economic reform, privatization, and civil liberties.