After the start of the Second World War, the commitments made by Germany towards the Baltic states under the secret protocol of August 23 could no longer satisfy the USSR. In Moscow, it was deemed necessary to take additional security measures and conclude mutual assistance agreements with the Baltic countries, providing for the deployment on their territory of separate Soviet military units.

On August 31, 1939, the Chairman of the Council of People's Commissars of the USSR and the People's Commissar for Foreign Affairs of the USSR V.M. Molotov made a statement in which he denied the existence of any agreements with Germany on the division of public interests. This was supposed to calm the political circles of Estonia, Latvia and Lithuania. The Soviet foreign policy in the Baltic direction at that time had a pronounced defensive nature, since the attempt to sovietize the Baltic could cause a sharp reaction from Britain and France. True, in the event of a rejection by the Baltic republics of the Soviet proposal for the conclusion of mutual assistance pacts, Moscow also had a military alternative. However, it did not come to that.

On September 28, 1939, a mutual aid pact between the CCPR and the Republic of Estonia was signed. The contracting parties committed themselves to provide each other with all kinds of assistance, including military, in the event of an attack or threat of attack from any great European power. The USSR also pledged to assist Estonia with supplies of military materials on preferential terms. The Soviet Union received the right to have on the Estonian islands of Saaremaa and Hiiumaa, as well as in the ports of Paldiski and Tallinn, the bases of the Navy and several airfields on loan terms.

The protocol stipulated that the total number of Soviet garrisons in Estonia at the time of the war in Europe would not exceed 25 thousand people. On October 5, a mutual aid pact between the USSR and Latvia was signed. Its text basically coincided with the text of the Soviet-Estonian agreement. On October 10, a mutual assistance agreement was concluded between the Soviet Union and Lithuania. According to the protocol, its ancient capital Vilna (Vilnius), seized by Poland in 1920 and ceded to the USSR in September 1939, was transferred to Lithuania. The number of Soviet troops in Lithuania was determined to be 20 thousand people. Almost simultaneously with the signing of mutual assistance pacts, the Soviet Union resumed trade agreements with the Baltic countries. Soviet bids brought them indisputable economic benefits.

The policy of Moscow’s non-interference in the internal affairs of the Baltic states at that time was very clear. Molotov, for example, demanded to stop there "all sorts of advances and communication with left circles." In one of the documents addressed to the employees of the Soviet plenipotentiary and the military attache in Lithuania, he strictly stated: "I categorically forbid interfering in inter-party affairs in Lithuania, supporting any opposition movements, etc. The slightest attempt by any of to interfere in the internal affairs of Lithuania will entail the strictest punishment of the guilty ... It should be rejected as provocative and harmful chatter about the Sovietization of Lithuania. "

In the order of the People's Commissar of Defense of October 25, 1939, given in connection with the entry of parts of the Red Army into the Baltic States, the personnel were required "not to interfere in any way in the internal affairs" of Estonia, Latvia, and Lithuania, and any conversations among military men about The "Sovietization" of these countries should have been stopped "in the most merciless way." Moscow adhered to this line because the Baltic countries had friendly relations with England and France. More active actions of the USSR in this region could not be regarded in London and Paris as hostile and directed against the great European powers. The uncertainty of the situation during the war in Europe forced Stalin’s diplomacy to a certain point not to force events.

The situation changed dramatically by the summer of 1940. The quick victory of Germany in the spring campaign of 1940 on the "Western Front" meant that Hitler got freedom of action against the USSR. There was a real threat of the Fuhrer's thesis: "If I achieve my goals in the West - I will change my course abruptly and attack Russia. No one can keep me from this. ”Under the circumstances, the USSR needed to think about strengthening its Western defensive ru-beyah. In Stalin’s understanding and his inner circle, this meant the inclusion of new territories into the USSR and the subsequent deployment of Soviet troops there.

By the summer of 1940, pro-Soviet governments were formed in the Baltic republics. On July 21-22, the Seimas of Lithuania and Latvia and the Estonian State Duma adopted declarations on state power and on the entry of these countries into the USSR. On August 3-6, 1940, the Supreme Soviet of the USSR, after hearing statements from specially authorized representatives of these countries to Moscow, adopted laws on the accession of Latvia, Lithuania and Estonia to the Union of Soviet Socialist Republics as union republics.