The history of Georgia can be traced back to the ancient kingdoms of Colchis and Iberia, and it was one of the first countries to adopt Christianity, in the 4th century. Georgia reached the peak of its political and economic strength during the reign of King David and Queen Tamar in 11th and 12th century. At the beginning of the 19th century, Georgia was annexed by the Russian Empire. After a brief period of independence following the Russian Revolution of 1917, Georgia was annexed by Russian red army in 1921 and in 1922 Georgia was incorporated into the Soviet Union.