Greece is considered the cradle of Western civilization, being the birthplace of democracy, Western philosophy, the Olympic Games, Western literature, historiography, political science, major scientific and mathematical principles, and Western drama. From the eighth century BC, the Greeks were organised into various independent city-states, known as poleis (singular polis), which spanned the entire Mediterranean region and the Black Sea. Philip of Macedon united most of the Greek mainland in the fourth century BC, with his son Alexander the Great rapidly conquering much of the ancient world, spreading Greek culture and science from the eastern Mediterranean to the Indus River. Greece was annexed by Rome in the second century BC, becoming an integral part of the Roman Empire and its successor, the Byzantine Empire, wherein the Greek language and culture were dominant. The Greek Orthodox Church also shaped modern Greek identity and transmitted Greek traditions to the wider Orthodox World. Falling under Ottoman dominion in the mid-15th century, the modern nation state of Greece emerged in 1830 following a war of independence. Greece's rich historical legacy is reflected by its 18 UNESCO World Heritage Sites, among the most in Europe and the world.
Greece achieved independence from the Ottoman Empire in 1830. During the second half of the 19th century and the first half of the 20th century, it gradually added neighboring islands and territories, most with Greek-speaking populations.
In World War II, Greece was first invaded by Italy (1940) and subsequently occupied by Germany (1941-44); fighting endured in a protracted civil war between supporters of the king and other anti-communist and communist rebels. Following the latter's defeat in 1949, Greece joined NATO in 1952.
In 1967, a group of military officers seized power, establishing a military dictatorship that suspended many political liberties and forced the king to flee the country. In 1974 following the collapse of the dictatorship, democratic elections and a referendum created a parliamentary republic and abolished the monarchy. In 1981, Greece joined the EC (now the EU); it became the 12th member of the European Economic and Monetary Union (EMU) in 2001. Greece has suffered a severe economic crisis since late 2009, due to nearly a decade of chronic overspending and structural rigidities. Since 2010, Greece has entered three bailout agreements with the European Commission, the European Central Bank (ECB), the IMF, and with the third, the European Stability Mechanism (ESM). The Greek Government agreed to its current, $96 billion bailout in August 2015, which will conclude in August 2018.