A country of north-central Europe on the Baltic Sea. Settled perhaps as early as 1500 BC, the area was unified in the 1200s and became one of the largest states of medieval Europe. Lithuania merged with Poland in 1569 but was absorbed into Russia by three partitions of Poland (1772, 1793, and 1795). The independent country of Lithuania existed from 1918 to 1940, when it became a constituent republic of the USSR. Occupied by Germany from 1941 to 1944, it reverted to Soviet rule after World War II and was known as the Lithuanian Soviet Socialist Republic before achieving independence in 1991. Vilnius is the capital and the largest city.