The essence of the "Slavic program" of Hitler was formulated by the fascist dictator to the utmost briefly: "We must destroy the peoples as precisely as we must systematically take care of the German population. We must develop a technique for the extermination of peoples."

Starting on September 1, 1939 with World War II by attacking Poland, Hitler “achieved” that England and France declared war on Germany. On September 17, the Soviet leadership acquainted the Polish ambassador with a note stating that “the Polish government disintegrated and does not show signs of life. This means that the Polish state and its government virtually ceased to exist. Thus, the treaties concluded between the USSR and Poland. " Due to the current situation, the Soviet government ordered the command of the Red Army to cross the border and "take under their protection the lives and property of the population of Western Ukraine and Western Belarus." At the same time, for Moscow, it was important not only to strengthen the USSR border, but also to liquidate the statehood of Poland, which Stalin called the "fascist state".

On September 17, 1939, units of the Red Army crossed the border of Poland , meeting no resistance on their way. During this campaign, the territory of the USSR increased by 196 thousand square meters. km, and the population - 13 million people.

The reaction of the foreign public to the fact of the entry of Soviet troops in Western Ukraine and Western Belarus, captured by Poland in 1920, was different. But at the official level, both in London and in Paris they decided that the West "is not obliged to go to war with the USSR".

The international situation, despite the signing in 1939 of treaties between Germany and the USSR, continued to deteriorate. In the spring of 1940, Romania expressed the wish "to strengthen and expand cooperation between Germany and Romania" in all areas. Under these conditions, the Soviet government decided to immediately resolve the issue of the reunification of Bessarabia, which was seized by Romania in early 1918 during military intervention.

Moscow informed Berlin of its intentions. On June 25, the German government, through Ambassador Schulenburg, announced that it "fully recognizes the right of the Soviet Union to Bessarabia." After this, Molotov, in an ultimatum tone, suggested to the Romanian envoy to fulfill the requirements of the USSR. On June 28, 1940, Soviet troops under the command of G. K. Zhukov entered the territory of Bessarabia and Northern Bukovina. The border of the USSR was moved more than 200 km to the west of the Dniester and now ran along the Prut and Danube rivers. This seriously improved the strategic situation on the south-western borders of the country.

However, the situation remained extremely tense. The Kremlin soon became aware of the statement of the German military, who sought to reassure the Romanian leadership: "Give the Soviet Union everything he asks. In a few months, we will help you take everything back with the addition of territory." Germany signed a series of economic agreements with Romania, sent there its military mission to prepare the army for war against the USSR. Parts of the Wehrmacht appeared in Romania. The situation on the Balkan Peninsula exacerbated with each new step of Germany. At the beginning of 1941 it became clear that the next country to fall into the orbit of the influence of the Reich would be Bulgaria. On March 1, she joined the tripartite pact - the military alliance of Germany, Italy and Japan.

German troops dispersed in southern Bulgaria, preparing for further aggressive actions.

In accordance with the plans of Hitler to the tripartite pact was supposed to join Southeast Asia. However, the government of Yugoslavia went to rapprochement with Moscow, saying that it was ready to immediately "take on its territory any armed forces of the USSR, first and foremost aviation." During the negotiations held in the Kremlin early in the morning of April 6, 1941, the Soviet-Yugoslav treaty was signed. Its essence was that the parties committed themselves not to attack each other and respect the independence, sovereign rights and territorial integrity of the USSR and Yugoslavia. In the event that one of the contracting parties was attacked by a third state, the other contracting party had to "comply with the policy of friendly relations with it".

However, hopes for a concluded agreement were not justified. Stop the aggression of Germany in the Balkans failed. After just a few hours after the signing of the agreement of April 6, Wehrmacht troops invaded Yugoslavia and Greece, occupying these countries. Germany’s position in southeastern Europe has been greatly strengthened. In the Balkans, a bridgehead was created to attack the USSR. The Soviet leadership, despite the alarming course of events, until the beginning of the war with Germany could not believe in the inevitability of German aggression.