The establishment of a Polish state is often identified with the adoption of Christianity by its ruler Mieszko I in 966, when the state covered territory similar to that of present-day Poland. Poland became a kingdom in 1025, and in 1569 it cemented a long association with the Grand Duchy of Lithuania by uniting to form the Polish-Lithuanian Commonwealth. The Commonwealth collapsed in 1795, and its territory was partitioned among Prussia, Russia, and Austria. Poland regained its independence in 1918 after World War I but lost it again in World War II, occupied by Nazi Germany and the Soviet Union. Poland lost over 6 million citizens in WWII, and emerged several years later as a socialist republic within the Eastern Bloc under strong Soviet influence. In 1989 communist rule was overthrown and Poland became what is constitutionally known as the "Third Polish Republic". Poland is a unitary state made up of sixteen voivodeships (Polish: województwo). Poland is also a member of the European Union, NATO and OECD.
The total area of Poland is 312,679 km² (120,728 sq mi), making it the 69th largest country in the world and 9th in Europe. Poland has a population of over 38.5 million people, which makes it the 33rd most populous country in the world. Poland's territory accounts for 1.4 percent of Europe's total surface area, and for 0.23 percent of the world's land masses. Poland is 120 times bigger than Liechtenstein and 520 times bigger than Singapore. The Voivodeship of Greater Poland (Wielkopolska) is exactly the size of Belgium. Poland lies in the central part of the European continent, the geometrical centre of which is near Warsaw. Before the Partitions (late 18th century) it was about 733,000 sq km. Partitioned and annexed by Russia, Prussia and Austria, in 1795 Poland disappeared from the map of Europe for the next 123 years. On the restoration of independence in 1918 it covered 388,000 sq km.
Poland's population stands at 38,500,000. This figure makes it the 29th most populated country in the world and the 8th in Europe. Poles account for 5.3 percent of all Europeans and for 0.65 percent of the world's population. Norway, whose area is nearly the same as Poland's (323,900 sq km), has 8.5 times fewer residents. The Opole province, Poland's smallest, is four times more populated than Iceland. Poles are one of Europe's youngest societies - half of the nation is below the age of 35. At the same time our country holds second place in terms of number of students.
Poland is a democracy, with a President as a Head of State, whose current constitution dates from 1997. The government structure centres on the Council of Ministers, led by a prime minister. The president appoints the cabinet according to the proposals of the prime minister, typically from the majority coalition in the Sejm. The president is elected by popular vote every 5 years. Polish voters elect a bicameral parliament consisting of a 460-member lower house (Sejm) and a 100-member Senate (Senat). With the exception of ethnic minority parties, only candidates of political parties receiving at least 5% of the total national vote can enter the Sejm. When sitting in joint session, members of the Sejm and Senate form the National Assembly (the Zgromadzenie Narodowe). The National Assembly is formed on 3 occasions: when a new President takes the oath of office; when an indictment against the President of the Republic is brought to the State Tribunal (Trybunał Stanu); and when a President's permanent incapacity to exercise his duties due to the state of his health is declared. To date, only the first instance has occurred.