places and retaliation of the Hungarian forces was labelled war crimes such as Ip and Treznea massacres in Northern Transylvania (directed against Romanians) or Bačka, where Hungarian military between 1941 and 1944 deported or killed 19,573 civilians, mainly Serbs and Jews, but also Hungarians who did not collaborate with the new authorities. About 56,000 people were also expelled from Bačka. The Jewish population of Hungary and the areas it occupied were partly diminished as part of the Holocaust. Tens of thousands of Romanians fled from Hungarian-ruled Northern Transylvania, and vice versa. After the war the areas were returned to neighboring countries and Hungary's territory was slightly further reduced by ceding three villages south of Bratislava to Slovakia. Some Hungarians were killed both in Yugoslavia by Yugoslav partisans (the exact number of ethnic Hungarians killed by Yugoslav partisans is not clearly established and estimates range from 4,000 to 40,000; 20,000 is often regarded as most probable), and in Transylvania by the Maniu Guard towards the end of World War II. Modern era The following table lists areas with Hungarian population in neighboring countries today: During the Communist era, Marxist–Leninist ideology and Stalin's theory on nationalities considered nationalism to be a malady of a bourgeois capitalism. In Hungary, the minorities' question disappeared from the political agenda. Communist hegemony guaranteed a facade of inter-ethnic peace while failing to secure a lasting accommodation of minority interests in unitary states. The fall of Communism aroused the expectations of Hungarian minorities in neighboring countries and left Hungary unprepared to deal with the issue. Hungarian politicians campaigned to formalize the rights of Hungarian minorities in neighboring countries, thus causing anxiety in the region. They secured agreements on the necessity for guaranteeing collective rights and formed new Hungarian minority organizations to promote cultural rights and political participation. In Romania, Slovakia, and Yugoslavia (now Serbia), former Communists secured popular legitimacy by accommodating nationalist tendencies that were hostile to minority rights. The latest controversy caused by the government of Viktor Orbán is when Hungary took the presidency over the EU in 2011 when the "historical timeline" features was presented – among other cultural, historical and scientific symbols or images of Hungary - an 1848 map of Greater Hungary, when Budapest ruled over large swathes of its neighbors. In May 2020 Prime Minister Orban created some waves in neighbouring nations with a historical map of Hungary the restoration of Greater Hungary.