Estonia has been inhabited from at least 9,000 BC, according to archaeological evidence. Ancient Estonians were among of the last European pagans to convert to Christianity after the Livonian Crusade in the 13th century, when they were forced to do so. During the late nineteenth and early twentieth centuries, after centuries of repeated domination by Germans, Danes, Swedes, Poles, and Russians, an identifiable Estonian national identity started to develop. Estonia gained independence from Russia in 1920 following a short War of Independence at the conclusion of World War I in which Estonians, commanded by General Laidoner, were forced to fight for their newly acquired independence from their former coloniser. Estonia, which had been democratic before to the Great Depression, was subjected to authoritarian control beginning in 1934, during the period known as the Era of Silence. During World War II, Estonia was frequently disputed and occupied by both Germany and the Soviet Union, and was eventually absorbed by the latter as the Estonian Soviet Socialist Republic (Estonian SSR). The de jure continuation of Estonia's state was maintained by diplomatic representations and the Estonian government in exile after the country lost its de facto independence to the Soviet Union in 1991. Its de facto independence was restored on the 20th of August, 1991, after the peaceful Singing Revolution that began in 1987.