Central and Eastern Europe Soviet Union; the independent states in former Yugoslavia (which were not considered part of the Eastern bloc); and the three Baltic states – Estonia, Latvia, Lithuania (which chose not to join the CIS with the other 12 former republics of the USSR). The CEE countries are further subdivided by their accession status to the European Union (EU): the eight first-wave accession countries that joined the EU on 1 May 2004 (Estonia, Latvia, Lithuania, Czech Republic, Slovakia, Poland, Hungary, and Slovenia), the two second-wave accession countries that joined on 1 January 2007 (Romania and Bulgaria) and the third-wave accession country that
2004 enlargement of the European Union 2004 enlargement of the European Union The 2004 enlargement of the European Union was the largest single expansion of the European Union (EU), in terms of territory, number of states, and population to date; however, it was not the largest in terms of gross domestic product. It occurred on 1 May 2004. The simultaneous accessions concerned the following countries (sometimes referred to as the "A10" countries): Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia. Seven of these were part of the former Eastern Bloc (of which three were from the former Soviet Union and four