Estonia, Lithuania and Latvia gained independence after the division of the Russian Empire in 1918-1920. Opinions on the inclusion of the Baltic states in the USSR differ. Some call the events of 1940 a violent seizure, others - actions within the borders of international law.
Background
To understand the issue, you need to study the European situation of the 30s. When Hitler came to power in Germany in 1933, the Baltic States fell under the influence of the Nazis. The USSR, having a common border with Estonia and Latvia, rightly feared the Nazi invasion through these countries.
The Soviet Union invited European governments to conclude a common security treaty immediately after the Nazis came to power. Soviet diplomats were not heard; the contract did not take place.
The diplomats made the next attempt to conclude a collective agreement in 1939. Throughout the first half of the year, negotiations were held with the governments of European states. The agreement did not take place again due to divergence of interests. The French and British, who already had a peace treaty with the Nazis, were not interested in preserving the USSR, they were not going to hinder the advance of the Nazis east. The Baltic countries, which had economic ties with Germany, preferred Hitler's guarantees.
The government of the USSR was forced to make contact with the Nazis. On August 23, 1939 in Moscow between Germany and the USSR, the Nonaggression Treaty, known as the Molotov-Ribbentrop Pact, was signed.
The entry of Soviet troops into Poland
On September 1, 1939, the troops of the Third Reich crossed the Polish border.
On September 17, the USSR government took a retaliatory step and sent troops into Polish territories. USSR Foreign Minister V. Molotov explained the introduction of troops by the need to protect the Ukrainian and Byelorussian population of Eastern Poland (aka Western Ukraine and Western Belarus).
The previous Soviet-German partition of Poland moved the borders of the Union to the West, the third Baltic country, Lithuania, became a neighbor of the USSR. The government of the Union began negotiations on the exchange of part of the Polish lands for Lithuania, which Germany saw as its protectorate (dependent state).
Unreasonable speculation about the upcoming division of the Baltic states between the USSR and Germany divided the governments of the Baltic countries into two camps. Supporters of socialism had hoped to maintain independence on the USSR, the ruling bourgeoisie advocated rapprochement with Germany.
Contract signing
This place could become Hitler's bridgehead for the invasion of the Soviet Union. An important task, for the implementation of which a whole range of measures was taken, was the inclusion of the Baltic countries in the USSR.
The Soviet-Estonian Mutual Assistance Pact was signed on September 28, 1939. It provided for the USSR’s right to have a fleet and airfields on Estonian islands, as well as the introduction of Soviet troops into Estonia. In return, the USSR committed itself to assisting the country in the event of a military invasion. On October 5, the Soviet-Latvian Treaty was signed on the same terms. On October 10, an Agreement was signed with Lithuania, which received Vilnius, recaptured by Poland in 1920, and received by the Soviet Union following the partition of Poland with Germany.
It should be noted that the Baltic population warmly welcomed the Soviet army, placing hopes on it for protection from the Nazis. The army was met by local troops with an orchestra and residents with flowers lined up along the streets.
The UK's most widely read newspaper, The Times, wrote about the lack of pressure from Soviet Russia and the unanimous decision of the Baltic population. The article noted that this option is a better alternative than inclusion in Nazi Europe.
The head of the British government, Winston Churchill, called the occupation of Poland and the Baltic by Soviet troops a necessity in protecting the USSR from the Nazis.
Soviet troops occupied the territory of the Baltic states with the approval of the presidents and parliaments of the Baltic states during October, November and December 1939.
Change of government
By mid-1940, it became clear that anti-Soviet sentiment prevailed in government circles in the Baltic states, and negotiations were ongoing with Germany.
In early June, the troops of the three closest military districts, under the subordination of the people's commissar of defense, were pulled along the borders of states. Secular diplomats presented ultimatums to governments. Accusing them of violating the provisions of the treaties, the USSR insisted on the introduction of a larger contingent of troops and the formation of new compositions of governments. Considering the resistance to be useless, the parliaments accepted the conditions, and during the period from June 15-17, additional troops entered the Baltic states. The only head of the Baltic states, the president of Lithuania, called on his government to resist.
The entry of the Baltic countries into the USSR
In Lithuania, Latvia and Estonia communist parties were allowed, amnesty was declared a political prisoner. In an extraordinary government election, the majority of the population voted for the Communists. In the West, the 1940 elections are called not free, violating constitutional rights. The totals are considered falsified. The formed governments decided to become part of the USSR and proclaimed the creation of three union republics. The Supreme Council of the Soviet Union approved the entry of the Baltic states into the USSR. However, now the Balts are sure that they were literally captured.
Baltic States as part of the USSR
From what year should Latvia, Estonia and Lithuania be considered an official part of the Soviet Union? Undoubtedly, since 1940, when they were included in the Union as the Latvian, Estonian, and Lithuanian SSR.
When the Baltic states became part of the USSR, reorganization of the economy followed. Private property was seized in favor of the state. The next stage was repression and mass deportations, the motivation for which was the presence of a large number of unreliable populations. Affected politicians, military, priests, bourgeoisie, prosperous peasantry.
Harassment contributed to the emergence of armed resistance, which finally took shape during the occupation of the Baltic states by Germany. Anti-Soviet formations collaborated with the Nazis, participated in the destruction of civilians.
Most of the economic assets of countries stored abroad were frozen when the Baltic states became part of the USSR. The British government returned to the Soviet Union only part of the gold purchased by the USSR State Bank before joining in 1968. The UK agreed to return the remaining funds in 1993, after Estonia, Latvia and Lithuania gained independence.
International assessment
When the Baltic states became part of the USSR, an ambiguous reaction followed. Some have recognized affiliation; some, for example the USA, did not recognize.
Churchill wrote in 1942 that Great Britain recognized the actual, but not legal borders of the USSR, and evaluated the events of 1940 as an act of aggression on the part of the Soviet Union and the result of an agreement with Germany.
In 1945, the heads of state of the Allies for the anti-Hitler coalition recognized the borders of the Soviet Union as of June 1941 during the Yalta and Potsdam conferences.
The Helsinki Security Conference, signed by the heads of 35 states in 1975, confirmed the inviolability of the Soviet borders.
The point of view of politicians
Lithuania, Latvia and Estonia declared independence in 1991, the first to declare their desire to leave the Union.
Western politicians call the inclusion of the Baltic states in the USSR occupation lasting half a century. Or occupations, followed by annexation (forced accession).
The Russian Federation insists that at the time when the Baltic countries became part of the USSR, the procedure was consistent with international law.
Citizenship issue
When the Baltic states became part of the USSR, the question of citizenship arose. Lithuania immediately recognized the citizenship of all residents. Estonia and Latvia recognized citizenship only of those who lived on the territory of pre-war states or their descendants. Russian-speaking immigrants, their children and grandchildren had to go through the legal process of acquiring citizenship.
Difference of views
Considering the statement about the occupation of the Baltic states, it is necessary to recall the meaning of the word "occupation". In any dictionary, this term means forced occupation of the territory. In the Baltic version of the annexation of territories there were no violent actions. Recall that the local population met the Soviet troops with enthusiasm, hoping for protection from Nazi Germany.
The statement about the falsified results of the parliamentary elections and the subsequent annexation (forced accession) of the territories is based on official data. They show that the turnout at the polls was 85-95% of the voters, 93-98% of the voters voted for the Communists. It should be borne in mind that immediately after the introduction of troops, Soviet and communist sentiments were quite widespread, but still the results were unusually high.
On the other hand, one cannot but take into account the threat of the use of military force by the Soviet Union. The governments of the Baltic countries rightly decided to give up resistance to superior military power. Orders for the ceremonial reception of Soviet troops were given in advance.
The formation of armed gangs that sided with the Nazis and operated until the beginning of the 50s confirms the fact that the Baltic population was divided into two camps: anti-Soviet and communist. Accordingly, part of the people perceived accession to the USSR as liberation from the capitalists, part as occupation.