Greece was the centre of ancient civilization, which influenced greatly the later European civilizations, both East and West. When the apostles Paul and Timothy brought the gospel to Greece, it was part of the Roman empire, which became the Byzantine empire from where Orthodox Christianity spread to Central and Eastern Europe. Greece was occupied by the Ottoman empire in the 16th century. It won its independence from the Ottomans in 1821, and became a monarchy. The history of Greece in the 19th and the first part of the 20th century was dominated by the national question, i.e. to extend the territory so as to include all Greeks. This policy succeeded before and during World War I in parts of the Balkans, but in Turkey the Greeks were defeated in 1922 and more than a million were expelled. In turn, 500,000 Turks were sent back from Greece to Turkey. This history explains the still persisting tensions between Greece and Turkey, although relationships have greatly improved. After a period of military dictatorship, democratic elections and a referendum created a parliamentary republic in 1974, and the monarchy was abolished. Greece joined the then European Community (now European Union) in 1981. Its economy has benefitted from the regional aid programmes of the EU. The Greek Orthodox Church is inextricably bound up with the Greek people, nation, state, culture and history. Catholics, Protestants, and Pentecostals represent about 1.5 percent. The largest independent group are the Orthodox Old Calendarists. In recent years, the Greek society has become more and more pluralistic.