The Vikings inhabited the territory of Estonia in the 9th century. The Middle Ages was the period, characterized by constant disputes and rival territorial claims between Denmark, Sweden, Poland and Russia. In the 16th-17th centuries Estonia got under Swedish imperial power, then the country was fully acquired by the Russians. After World War I Soviet government at last recognized Estonian independence. But under the Nazi-Soviet Pact of 1939 the Soviet Union took control of Estonia until it was conquered during the German invasion. In 1944 Estonia was proclaimed as one of the 15 Soviet Socialist Republics. In March 1990 the Estonian Communist Party voted in favor of full independence from the Soviet Union. Two years later the country’s own currency the Kroon was introduced. In July 1997 the country became an associate member of the EU. Nowadays Estonia has one of the best standards of living in the former Eastern bloc.