Prior to becoming a parliamentary republic in 1918, Latvia as an independent country has not really existed since the 13th century, despite maintaining it's cultural and linguistic distinctiveness. In the 13th century it was conquered by the Germans, in the 16th-18th centuries it was under Polish rule, and from the 18th century it was part of the Russian Empire. It did have a brief 20 year period of independence from 1918 to 1940 before being forcibly incorporated into the USSR, invaded and occupied by the Nazi's in 1941, and then reoccupied by the Soviet Union in 1944. It has only truly existed as an independent nation since 1991 with the break up of the Soviet Union.