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 has acted as Moldova's governing coalition since. Moldova experienced significant political uncertainty between 2009 and early 2012, holding three general elections and numerous presidential ballots in parliament, all of which failed to secure a president. Following November 2010 parliamentary elections, a reconstituted AEI-coalition consisting of the Liberal Democratic Party, the Liberal Party, and the Democratic Party formed a government, and in March 2012 were finally able to elect an independent as president.