There was no such harsh winter for about 50 years. Already in November 30 degree frosts hit, and in January the air temperature dropped to 40-45 degrees below zero. And this weather lasted until March. The frozen ground resembled concrete, and centuries-old pine trees burst from such frosts along their entire length with a sound resembling a gun’s shot. Nature did not regret the snow that fell almost every day. Such an inhospitable winter was in 1939-1940 in the north of the USSR and in Finland. And it was then that the Soviet leadership decided to punish the “presumptuous white Finns” with the hands of the Red Army. So on November 30, the “non-famous” Soviet-Finnish war of 1939-1940 began, which was then called the “liberation campaign”.
On August 23, 1939, a non-aggression pact was signed between Germany and the USSR. And this document also had a secret supplement. According to him, the two great powers divided their spheres of influence, and Finland fell under the “wing” of the Soviet Union, among other states. Meanwhile, since March 1938, the government of the USSR was negotiating with the government of Finland on joint actions to strengthen the sea and land borders of both states. The prerequisite for these negotiations was the German occupation of Austria and the complication of the political situation in Europe. The Soviet side first wanted to receive guarantees that no enemy would pass through Finnish territory and could not threaten Leningrad from that side. But the Finnish government refused such offers, and thus took a step towards making the Finnish war inevitable.
However, soon the Finns themselves realized how short-sighted such a refusal was, and began to feverishly arm themselves. Then the chairman of the Council of Defense was Marshal Mannerheim. And from its submission, the Finnish military-industrial complex has earned "to the fullest." The Finnish military paid special attention to strengthening and modernizing the defensive structures that had previously been erected on the Karelian Isthmus. And after Germany occupied Czechoslovakia (April 1939), a new round of negotiations began with the initiative of the USSR. This time, the Soviet leadership offered Finland military assistance in case of aggression. And in response, the Finns were to lease to the Union several islands located in the Gulf of Finland. On them, the military leadership of the Union planned to equip additional bases for covering Kronstadt from the sea. And although Mannerheim urged politicians to accept the proposal of the USSR, his opinion was ignored. After that, a peaceful resolution of the contradictions between the parties became impossible, and the Soviet-Finnish war was only a matter of time.
A non-aggression pact with Germany for some time untied the Soviet Union, and Moscow decided to occupy Finland. The formal occasion, after which the Finnish war of 1939 began, was the shelling of the positions of the Red Army near the village of Mainil. This happened on November 26, and the NKVD officers, acting under the guise of Finnish troops, carried out this provocation. After that, all kinds of diplomatic relations were broken between the countries, and on November 30 a large-scale invasion of the Red Army began on the territory of a neighboring state. The military leadership of the USSR planned within three weeks to defeat the Finnish army and occupy Helsinki.
But the plans of the Soviet military commanders were not destined to go astray. The frontal assault on the famous Mannerheim line failed. Then Soviet propaganda attributed this failure to the impregnability of this defense system. Although in reality the Finnish fortifications built on the Karelian Isthmus were 10 times weaker than the French Maginot line in terms of the number of bunkers, pillboxes and artillery weapons. And in fact, the Mannerheim Line was not an insurmountable obstacle for the then armies. Nevertheless, the Red Army did not even break the first line of Finnish positions in the first three weeks, not to mention the occupation of Helsinki. And on December 21 this attack completely stopped, and on the 26th of the same month the Red Army went over to the defensive. The Finnish war threatened to become protracted.
After that, an attempt was made to deliver an auxiliary strike to the Finnish positions north of Lake Ladoga. But this attempt ended in failure, and as a result, two “red” divisions were surrounded and completely defeated. In general, in that area, the Finns surrounded and destroyed five divisions of the Red Army. And again, Soviet troops began to advance only on February 1, 1940, after they received substantial reinforcements. Now the Northwest Front, commanded by S.K., has set its sights on Mannerheim’s line. Tymoshenko. It included the 7th and 13th armies. Daily artillery shelling weakened the defense of the Finns. And only on February 11 the defense of the Finns faltered. And on February 14, the Red Army took the city of Sum.
Thus, the Red Army slowly moved forward, and in March battles for the city of Vyborg had already begun. Now, the Finnish government, seeing the futility of further resistance, sent a delegation to Moscow for peace talks. They took 4 days, and on March 13 all military operations were stopped. The Finnish war ended, and the government of this country accepted all the conditions that the Soviet leadership had offered them. As a result of such a difficult victory, the USSR received the city of Vyborg, the entire Karelian Isthmus and the region located north of Ladoga, together with the city of Sortavala. Thus, it was possible to push the border away from Leningrad by 150 kilometers, although Finland still could not be annexed to the USSR. And the Finns as a result of this war lost all their defenses and remained virtually defenseless.