The fate of Estonia was decided by the German-Soviet Nonaggression Pact of August 1939 between Nazi Germany and the U.S.S.R. On September 28 the Soviet government imposed on Estonia a treaty of mutual assistance that conceded to the Soviet Union several Estonian military bases, which were occupied forthwith. A broadly based nonpolitical government under Juri Uluots was appointed, but on June 16, 1940, a Soviet ultimatum demanded a new Estonian government, “able and willing to secure the honest application of the Soviet-Estonia mutual assistance treaty.” The following day, Soviet forces occupied the whole country. On July 21 the Chamber of Deputies was presented with a resolution to join the U.S.S.R.; it was unanimously adopted the next day in spite of being contrary to constitutional procedure. On August 6 the Moscow Supreme Soviet incorporated Estonia into the U.S.S.R. as one of its constituent republics. Meanwhile, Päts, Laidoner, and many other political leaders were arrested and deported to the U.S.S.R. In the first 12 months of Soviet occupation, more than 60,000 persons were killed or deported; more than 10,000 were removed in a mass deportation during the night of June 13–14, 1941.

On June 22, 1941, Germany attacked the U.S.S.R. Large areas of Estonia were freed from Soviet forces by improvised Estonian units before the German army reached Estonia. For three years Estonia was under German occupation, becoming part of the Ostland province. By February 1944, however, the Russians were back on the Narva front. About 30,000 Estonians escaped by sea to Sweden and 33,000 to Germany; many thousands perished at sea. On September 22, 1944, Soviet troops took Tallinn.

Soviet republic

The first postwar decade was a particularly difficult period of repression and Russification. The efforts of the regime to restructure the country in a Soviet mold rendered national political and cultural life virtually impossible. Mass deportations occurred in several waves, most significantly in 1949 during the campaign to collectivize agriculture. It has been estimated that as many as 80,000 Estonians were deported between 1945 and 1953. Massive immigration from Russia and other parts of the U.S.S.R. decreased the indigenous proportion of the population. Before the war ethnic Estonians made up almost 90 percent of the population. By 1990 the proportion had sunk to about 60 percent. The ruling Communist Party was disproportionately immigrant in character. A large-scale purge in 1950–51 left virtually no native Estonian officials in the highest positions. The situation changed somewhat in the late 1950s and early 1960s, but by the late 1980s the ruling elite was still heavily immigrant.

The Soviet liberalization campaign of the late 1980s provided an opportunity for a national renaissance. In April 1988 an opposition Popular Front emerged. On June 16 the incumbent first party secretary, Karl Vaino, an immigrant, was dismissed. In the fall of 1988 the Popular Front pushed his successor, Vaino Väljas, to guide a resolution on sovereignty through the legislature. In the face of Soviet protests and warnings, Estonian law took precedence over Soviet legislation.

Independence restored

Proponents of independence won a clear victory in the March 1990 elections. On March 30, 1990, the Estonian legislature declared a transitional phase to independence. Independence was declared formally in August 1991 and was recognized by the Soviet Union the following month.

In June 1992 a new constitution was adopted, and in September legislative and presidential elections were held, with Lennart Meri, who was supported by the Isamaa (Fatherland) alliance, elected president. Among the key issues for independent Estonia were the rights of those residents of the republic who had immigrated after the Soviet annexation of Estonia in 1940. These nonethnic Estonians (mostly ethnic Russians) were required to apply for citizenship, with naturalization requirements including proficiency in the Estonian language. Relations between Russia and Estonia were strained over this issue and over the continued presence in Estonia of Russian troops, which finally left the country in August 1994.

Despite allegations of corruption and abuse of power by some top officials, by the end of the 1990s Estonia had developed a stable democracy. Although affected by the Russian financial crisis of 1998, Estonia’s economy was fairly robust throughout much of the late 1990s, and it strengthened even more in the opening years of the 21st century. In 2006 Toomas Hendrik Ilves became president. Ruled from 2005 to 2014 by a coalition led by the Estonian Reform Party and Prime Minister Andrus Ansip, the government responded to the challenges of the European financial crisis with an austerity program that kept the country’s economy strong enough for Estonia to join the euro zone in 2011. Ansip, his personal popularity slipping, stepped down in February 2014. He was succeeded as prime minister by Taavi Rõivas, who formed a coalition government with the centre-left Social Democratic Party. In foreign affairs, the country sought to improve its often tense relations with Russia and reoriented itself toward the West. In 1999 Estonia joined the World Trade Organization (WTO), and in 2004 it became a full member of both the North Atlantic Treaty Organization (NATO) and the European Union (EU).