Part of Romania during the interwar period, Moldova was incorporated into the Soviet Union at the close of World War II. Although the country has been independent from the USSR since 1991, Russian forces have remained on Moldovan territory east of the Dniester River supporting a Transnistrian separatist region with a Slavic majority population of mostly Ukrainians and Russians. One of the poorest nations in Europe, Moldova became the first former Soviet state to elect a Communist, Vladimir VORONIN, as its president in 2001. VORONIN served as Moldova's president until he resigned in September 2009, following the opposition's gain of a narrow majority in July parliamentary elections and the Communist Party's (PCRM) subsequent inability to attract the three-fifths of parliamentary votes required to elect a president. Moldova's four opposition parties formed a new coalition, the Alliance for European Integration (AEI), which acted as Moldova's governing coalition until December 2010. Moldova has experienced significant political uncertainty since 2009, holding three general elections (in April 2009, July 2009, and November 2010) and four valid presidential ballots in parliament, all of which failed to secure a president. Following the November 2010 parliamentary elections, a reconstituted AEI-coalition consisting of the Liberal Democratic Party, the Liberal Party, and the Democratic Party formed a government, but remains three votes short of the three-fifths majority required to elect a president.