The battles on the Eastern Front constituted the largest military confrontation in history. They were characterized by unprecedented ferocity, wholesale destruction, mass deportations, and immense loss of life variously due to combat, starvation, exposure, disease, and massacres. The Eastern Front, as the site of nearly all extermination camps, death marches, ghettos, and the majority of pogroms, was central to the Holocaust. Of the estimated 70 million deaths attributed to World War II, over 30 million, many of them civilians, died on the Eastern Front. The Eastern Front was decisive in determining the outcome of World War II, eventually serving as the main reason for Germany's defeat. It resulted in the destruction of the Third Reich, the partition of Germany for nearly half a century and the rise of the Soviet Union as a military and industrial superpower.
The two principal belligerent powers were Nazi Germany and the Soviet Union, along with their respective allies. Though never engaged in military action in the Eastern Front, the United Kingdom and the United States both provided substantial material aid to the Soviet Union. The Sovietâ€“Finnish Continuation War may be considered the northern flank of the Eastern Front. In addition, the joint Germanâ€“Finnish operations across the northernmost Finnishâ€“Soviet border and in the Murmansk region are also considered part of the Eastern Front.
Despite their ideological antipathy, both Germany and the Soviet Union shared a mutual dislike for the outcome of World War I. The Soviet Union had lost substantial territory in eastern Europe as a result of the treaty of Brest-Litovsk, where it gave in to German demands and ceded control of Poland, Lithuania, Estonia, Latvia and Finland, among others, to the "Central Powers". Subsequently, when Germany in its turn surrendered to the Allies, these territories were liberated under the terms of the Paris Peace Conference of 1919 Russia was in a civil war condition, the Allies did not recognize the Bolshevik government, and the Soviet Union would not be formed for another 4 years so no Russian representation was present.
The Molotov-Ribbentrop Pact signed in August 1939 was a non-aggression agreement between Nazi Germany and the Soviet Union that contained a secret protocol that aimed to return Central Europe to the preâ€“World War I status quo by dividing it between Germany and the Soviet Union. Finland, Estonia, Latvia and Lithuania would return to Soviet control, while Poland and Romania would be divided between them.
According to Andrew Nagorski (2007; The Greatest Battle) Adolf Hitler had declared his intention to invade the USSR on 11 August 1939 to Carl Jacob Burckhardt, League of Nations Commissioner by saying, "Everything I undertake is directed against the Russians. If the West is too stupid and blind to grasp this, then I shall be compelled to come to an agreement with the Russians, beat the West and then after their defeat turn against the Soviet Union with all my forces. I need the Ukraine so that they can't starve us out, as happened in the last war."
The two powers invaded and partitioned Poland in 1939. After Finland refused the terms of a Soviet pact of mutual assistance, the USSR invaded Finland in November 1939 in what became known as the Winter War â€“ a bitter conflict that only resulted in partial Soviet victory. In June 1940, the USSR occupied and illegally annexed the three Baltic statesâ€”an action in violation of the Hague Conventions (1899 and 1907) and numerous bi-lateral conventions and treaties signed between the USSR and Balticsâ€”and never recognized by most Western states. The Molotov-Ribbentrop Pact ostensibly provided security to Soviets in the occupation of both the Baltics and the north and northeastern regions of Romania (Northern Bukovina and Bessarabia)â€”although Hitler in announcing invasion of the USSR cited the Soviet annexations of Baltic and Romanian territory as having violated Germany's understanding of the Pact. The annexed Romanian territory was divided between the Ukrainian and Moldavian Soviet republics.