Ukraine was the center of the first eastern Slavic state, Kyivan Rus, which during the 10th and 11th centuries was the largest and most powerful state in Europe. Weakened by internecine quarrels and Mongol invasions, Kyivan Rus was incorporated into the Grand Duchy of Lithuania and eventually into the Polish-Lithuanian Commonwealth. The cultural and religious legacy of Kyivan 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 achieve a short-lived period of independence (1917-20), but was reconquered and forced to endure a brutal Soviet rule that engineered two forced 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 and prosperity remained elusive as the legacy of state control and endemic corruption stalled efforts at economic reform, privatization, and civil liberties. A peaceful mass protest "Orange Revolution" in the closing months of 2004 forced the authorities to overturn a rigged presidential election and to allow a new internationally monitored vote that swept into power a reformist slate under Viktor YUSHCHENKO. Subsequent internal squabbles in the YUSHCHENKO camp allowed his rival Viktor YANUKOVYCH to stage a comeback in parliamentary elections and become prime minister in August of 2006. An early legislative election, brought on by a political crisis in the spring of 2007, saw Yuliya TYMOSHENKO, as head of an "Orange" coalition, installed as a new prime minister in December 2007. Viktor YANUKOVUYCH was elected president in a February 2010 run-off election that observers assessed as meeting most international standards. The following month, the Rada approved a vote of no-confidence prompting Yuliya TYMOSHENKO to resign from her post as prime minister.