The Eastern Front is the generic name for the theater of operation during the Second Great War, that primarily involved the Soviet Union and her allies on one side, and the German Empire and her allies on the other side.
The first move in the Eastern Front was the invasion of western Poland by Germany, on September 1, 1939, followed soon by an invasion of eastern Poland by the Soviet Union as result of the Molotov–Ribbentrop Pact of no aggression between the German Empire and the Soviet Union.
This was soon followed by the invasion and annexation of Lithuania, Latvia, and Estonia by the Soviet Union and the attempt to invade Finland in what was known as the Winter War.
The Soviet Union also demanded Romania the Bessarabia territories and pushed Romania to break her neutrality. Romania did by setting an alliance with Germany.
The Soviet Union broke the Molotov–Ribbentrop Pact first by invading Germany, west Poland and Romania the 20 May, 1941. The surprise attack led to an initial Soviet advance, but the three fronts had varied results. By December 1941, Romania had surrendered to the Soviet Union and declared a pro-Soviet government, the Germans had reverted the invasion of West and East Prussia and had themselves invaded Lithuania, Latvia, and Estonia, while the Polish front had been stalled with heavy fights in the streets of Warsaw.
In mid December 1941, Soviet and Romanian troops moved into Hungary and Bulgaria, and set an effective defense of Leningrad.
The Hungarian Campaign
Early 1942 was dominated by fights in Hungary. Germany had already lost her allies Romania and Bulgaria, and was determined not to let another ally fall to the Soviets, while still fighting in Poland and the Baltic.
By June, 1942, most Hungary was controlled by Germany.
The Barbarrossa Offensive
In May 1942, Germany had concentrated some heavy troops in the Baltic and launched a final offensive, with the objective to take Leningrad and east Poland from the Baltic, and then move into the heart of Russia.
Vilnus felt on June 3. Minsk on June 8. Leningrad on June 30. Smolensk on August 3. Warsaw on August 9. Kiev on August 23.
Despite these great advances, Germany had several logistical problems in sustaining these offensives. By mid 1942, the Soviet Union were surpassing German's industrial production of war materials, and had better oil supplies. Germany was running low on oil. Kiev was recovered by the Soviets on September 5 after encircling the Germans, and the Barbarosa Offensive was practically stopped.
The Soviets decided not to counterattack Germany right away after the liberation of Kiev, but rather engage the Germans in constant harassment until the outcome of the winter. The Germans did very little to gain the invaded peoples, letting the way for partisans to constantly attack the German supply lines.
The Soviets engaged in the liberation of Yugoslavia, joined by British and Greek troops, who were also moving into Italian Albania and Montenegro.
In December 1942, the Soviets launched an massive offensive against German positions inside Russia and Ukraine, with better tanks and improved airplanes. The movements were slow for the winter, but the Soviets counted that the conditions would slow down even more the German mobility. In a few weeks, the Soviets freed Smolensk, Minsk, and Vilna, moving then north into Riga and southwest into Brest. From Lviv they launched an attack into Lubin and Krakow.
By mid February 1943 the Soviets had captured Riga cutting land lines to the Germans in Estonia and Leningrad, as well as Lubin and Krakow.
The massive insurrection in Yugoslavia, supported by both Britain and the Soviet Union, and a civil war that started in Italy, both in earlier March became a further concern to the Germans. The Soviets and Romanians invaded Slovakia, and moved into the German pockets in the Baltic. Leningrad was freed on March 26.
Soviet bombers begun to regularly fly over Berlin and other German cities. In April 15, a Soviet-British agreement coordinated the bombing campaign over Germany by the British attacking on nights and the Soviets on daylight.
Germany retired most of their troops from other fronts. Leaving just enough to protect the French coastline and the Hungarian-Romanian front, all her resources were concentrated on the Western Front.
In June 1943, Warsaw fall and the Soviet Union stopped their advance. Most Poland, Slovakia, Bulgaria, Romania, Lithuania, Latvia and Estonia, as well as the original Soviet land were controlled by the Soviet Union and her allies. The German resistance was fierce in defense of the German homeland. While a victory seemed possible for the Soviet Union, their decision was to secure the current territories and promote a communist government in Yugoslavia.
Germany Final Offensive
Germany situation was critical, mainly by the lack of good oil supplies. Germany had lost very important allies such as Romania and Yugoslavia, and Italy was about to fall. The Soviets had stopped their advance but they are fortifying their gains and preparing an offensive, plus they are still bombing German soil both from ground artillery and from the air.
It was clear that the Soviet Union were improving her tactics, and out competing Germany in terms of industrial production of war materials. Germany still had air superiority on the German skies, but they had no complete control as proved by the constant bombardments by both the Soviets and the British, and the Soviets were improving their planes too.
However Germany was the attacked power during Operation Thunderstorm. There were the Soviet Union the one breaking the Molotov-Ribbentrop Pact. So Germany begun a diplomatic offensive in order to get an agreement with Stalin. Stalin never received the German diplomats or allowed any higher official to talk with the Germans.
The time was not on the German side. German needed to have a winning position in order to secure their mere existence. In August 1943, Germany launched their last offensive. While keeping strong defensive positions in Prussia and Poland, Germany launched a massive attack into Slovakia and Romania with the objective to advance into Ukraine and the Black Sea.
In two weeks Slovakia was freed. And that was all. The Germans could not break the Soviet defenses in Romania and Ukraine. Then, in a slow movement, the Soviet Union retook Slovakia by November.
A long winter
In the winter from 1943 to 1944, the Soviet Union only moved slowly into securing all pre-1939 Poland, while keeping constant artillery attacks over the Soviet-German front and bombing German cities.
New Soviet fighter escorts had been proving to be better than German fighters. The Germany aviation was no longer the dominant power in German airspace.
Before the freezing session, the British had managed to capture Svalbard and Narvik, and since then they were practicing amphibian strategies in the Norwegian shore. Italy fascist regime fell in October, and while Germany managed to invade northern Italy, the pro-British Italian government controlled most of the Peninsula. The Mediterranean was a British lake during the winter. The Royal Navy also controlled the North Sea. Most of the British Navy in the Pacific and east Indian Ocean had been redeployed to the North Atlantic, as the Australian and New Zealand navies had joined the US Pacific Fleet to secure the possessions of the British Empire in southwest Asia.
By the end of the winter, Britain had been increasing their commando incursions in northern France, mainly near Calais. The Germans knew that that was the prelude to an invasion over the English channel.
And it was proved right on March 1944.
The Fall of the German Empire
The Soviet Union renewed her offensive in March 1944 just after the British had secured their beachheads in Belgium and Southern France. In a period of two weeks, Königsberg fell and Danzig was in siege by mid April. Hungary was invaded. Yugoslavia had declared a pro-Soviet government and begun their campaign supporting the soviet invasion of Hungary and moving into Northern Italy.
The 13 May, 1944, the announce was made: Adolf Hitler was killed, and most of the Nazi highest leaders had been arrested. General Rommel had been appointed the General Command of all German arms (except of Nazi paramilitaries, such as the SS, who were proscribed). A negotiated peace was offered to both Britain and the Soviet Union.
While Britain were demanding an unconditional surrender, they acceded to enter negotiations. German negotiators, sat with Soviet and British peers in Stockholm on May 25, 1944. A Truce was agreed effective June 1st.
The German government offered to retreat to 1939 borders, and to dissolve the Anschluss. Both Britain and the Soviet Union demanded also demilitarization of Germany. The Soviet Union demanded recognition of the pro-Soviet governments in occupied territories, as well as the incorporation of the Baltic republics, eastern Poland and Bessarabia into the Soviet Union. The Germans did not contest those demands, but the British insisted on the existence of Poland. Germany opposed to any initiative that would reduce German pre-war borders.
By mid July, the Wehrmacht has retired from France, Belgium, the Netherlands, Northern Italy, Norway, Denmark and any other pre-Anschluss territory. Some pro-Nazi governments still tried to control those territories with support of some SS, but the German negotiators in Stockholm rejected any link of the new German government with those parties. Soon Free France, backed by the British took control of France, Northern Italy surrendered to the Italian government in Rome, and Belgium, the Netherlands and Norway proclaimed pro-British governments.
Poland, and the demilitarization of Germany were the main unresolved problems in Stockholm.
Finally, Germany acceded on three main points: 1) Germany would be confined to pre-1937 borders. With Danzig and Breslau transferred to Poland. 2) The Anschluss was over. Germany and Austria would have separate governments. 3) Germany and Austria would demilitarize. Both Germany and Austria would be occupied by the United Kingdom, the Soviet Union, Poland, and France, however this occupation zones would not be annexed to any of these powers.
The Soviet Union acceded to 1) Retire from Poland west of the Curzon line, allowing the Polish government in exile to decide the Polish fate. 2) Not to annex the occupied zones in Germany or Austria into the Soviet Union or any other pro-soviet state.
Britain acceded to 1) Recognize the pro-soviet governments in Romania, Hungary, Bulgaria and Yugoslavia, and the annexation of the Baltic Republics, Bessarabia and eastern Poland into the Soviet Union.
The agreement of these points, on September 19, 1944, is declared as the end of the Second Great European War. And, for many, the beginning of the Cold War.