The position of the USSR and its role in the coalition changed after the battles of Stalingrad and Kursk, when the victories of the Red Army led to a radical change in the course of the war. The increased economic potential of the country and changes in domestic policy (liquidation of the Comintern, the introduction of the patriarchate on September 8, 1943, etc.) also contributed to strengthening the positions of the USSR and personally of IV Stalin in the allied coalition.

Even the use of the Katyn drama by the fascist Germany on April 13, 1943 (the destruction of 21 857 Polish prisoners of war in the USSR in 1940, including 4421 in Katyn) could not prevent the Allies from coming together, who were satisfied with the official version of the Germans responsible for shooting the Poles. The outcome of this process is the succession of the Moscow Conference of the three Foreign Ministers (October 19-30, 1943), the Tehran Conference of the Big Three (November 28 - December 1, 1943), the Yalta Conference (February 4-11, 1945) and Potsdam Conference (July 17 - August 2, 1945).

At the Moscow Conference, for the first time, with the participation of the USSR, questions of the post-war structure, including the German question, were considered. Its members agreed to create an organization that later became known as the United Nations (UN). The main outcome of the Tehran meeting of I. Stalin, F. Roosevelt and W. Churchill was the positive resolution of the question of opening a second front in northern France (Operation Overlord) during May 1944, with simultaneous support by the Allied troops in the south of France ( Operation Dragoon) and the strategic instigation of the Soviet Army on the Eastern Front. It was also confirmed the entry of the USSR after the capitulation of Germany in the war against Japan. The issues of postwar Germany and Poland, including their borders, were not finally resolved.

Implementing the decisions of the Tehran Conference, with some delay, the landing of the Allies in Normandy began on June 6, 1944, and Paris was already liberated on August 25, 1944. At the same time, the offensive launched by the Soviet troops in the north-west of Russia, in Finland (September 19, truce) and in Belarus (Operation Bagration from June 23 to August 29, 1944) continued on all fronts. Joint concerted actions of the Allies confirmed the effectiveness of the coalition and led to the collapse of the fascist bloc in Europe. Special attention should be paid to the interaction of the Allies during the Ardennes counteroffensive of Germany (December 16, 1944 - January 26, 1945), when Soviet troops earlier than the scheduled date (January 12, 1945) began, at the request of the Allies, an offensive from the Baltic Sea to the Carpathians, thus rescuing the Anglo-American troops from defeat in the Ardennes. It should be noted that in 1944-1945. The Eastern Front was still the main one: 150 German divisions were operating there, against 71 divisions and 3 brigades on the Western Front and 22 divisions in Italy.

Successful actions in 1944 led to the need to convene a new conference of the Allies on the eve of the surrender of Germany. The Yalta (Crimea) Conference addressed issues primarily related to the post-war structure of Europe. An agreement was reached on the occupation of Germany, its demilitarization, denazification and de-monopolization, on German reparations. France, as opposed to the United States, was allowed to occupy and govern Germany, except for the three great powers, at the suggestion of the USSR. It was decided to trial war criminals. The borders of Poland, in accordance with the decisions of the conference, were held in the east along the "Curzon Line" with compensation for territorial losses by acquisitions in the north-west at the expense of Germany. Thus, the accession to the USSR of Western Belarus and Ukraine was consolidated. Finally, questions were resolved about the timing of the institution and the structure of the UN, where, along with the USSR, Ukraine and Belo-Russia received representation. The USSR also confirmed its entry into the war with Japan.

At the same time, the campaign of 1945 revealed contradictions in the camp of the allies, primarily between the USSR and Great Britain. W. Churchill sought at all costs to reduce the political importance of the troubles of the Red Army, to minimize the penetration of the Soviets into Europe.

To this end, he tried to adjust the military plans of the Anglo-American forces at the beginning of 1945 towards an advance attack on Berlin. Only the position of US President F. D. Ruz-Welt and the commander of the American troops, General D. Eisenhower, prevented the Allied struggle for Berlin, on which W. Churchill and the English General B. L. L. Montgomery insisted. The objections of the American side were caused by the fear of additional casualties (at least 100,000 soldiers), US loyalty to the allied duty, the desire to play the role of an international arbiter in the post-war world, as well as economic and military-political (nuclear) interest in controlling South Germany. Of particular importance to the United States was also the support of the USSR for military action against Japan after the defeat of Germany.

After the capitulation of Germany on May 8, 1945, the authorities in the occupied territory passed to the governments of the USSR, the USA, Great Britain and France, who ruled the country through the created Control Council, military administrations in the zones of occupation and the inter-allied commandant's office of Berlin. The USSR made a decisive contribution to the defeat of the fascist bloc. The Soviet-German front throughout the Second World War was the main theater of operations. It was here that the Wehrmacht lost more than 73% of the personnel, up to 75% of tanks and artillery pieces, more than 75% of aviation.

From July 17 to August 2, 1945, the last meeting at the highest level during the war years took place in Potsdam, in which J. Stalin and G. Truman participated (replaced Roosevelt after his death on April 12, 1945 as president of the United States), Winston Churchill (since July 28, he was replaced by the leader of the winning Laborites C. Attlee). Germany had to pay $ 20 billion (50% of the USSR). Considering the total damage from the war of $ 125 billion, the USSR also received as compensation most of East Prussia with the city: Koenigsberg (since 1946 - Kaliningrad ), and Poland - the remaining territory. This also solved the Prussian problem - the center of German militarism. For the preparation of peace treaties with Germany, the allies at the conference created a permanent Council of Foreign Ministers. During the conferences, the American side attempted to exert political pressure on the USSR, using news of the successful testing of US atomic weapons as a means of pressure.