Though related to the people of Finland, the Ests of Estonia had been a colony of Denmark, the Teutonic Knights, Swedes, Poles, and Russians. And through it all, Germanic burghers ruled the towns of the region. The Ests, tied to the land, were primarily serfs (serfdom not being abolished until 1819). A nationalist spirit began to surface with interest in folklore, language, and history. In 1920, a fully independent Estonia emerged thanks to the 1918 Treaty of Brest-Litovsk. This period of independence came to a halt with the 1939 Hitler-Stalin pact as Estonia was given over to the Soviets as a sphere of influence. Soviet troops, far outnumbering the Estonia military, were garrisoned in the country. Elections in 1940 that were presumably rigged by the Soviet Union resulted in Estonia 'requesting' to be annexed into the USSR, a move that was never recognized by the US. Throughout the Second World War, Estonia endured huge losses through battle, deportation, flight, and outright murder. Not until 1990 did Estonia manage to begin the process of freeing itself. In 1991, Estonia's independence was recognized by the Soviets. Estonia, like its Balkan cousins, did not become part of the Commonwealth of Independent States.It joined both NATO and the EU in the spring of 2004, formally joined the OECD in late 2010, and adopted the euro as its official currency on 1 January 2011. It is one of the most successful former parts of the USSR.