The European theatre of World War II was one of the two main theatres of combat during World War II. It saw heavy fighting across Europe for almost six years, starting with Germany's invasion of Poland on 1 September 1939 and ending with the Western Allies conquering most of Western Europe, the Soviet Union conquering most of Eastern Europe including the German capital Berlin, and Germany's unconditional surrender on 8 May 1945 although fighting continued elsewhere in Europe until 25 May. On 5 June 1945, the Berlin Declaration proclaiming the unconditional surrender of Germany to the four victorious powers was signed. The Allied powers fought the Axis powers on two major fronts (Eastern Front and Western Front), but there were other fronts varying in scale from the Italian campaign (the 3rd largest campaign in Europe), to the Polish Campaign, as well as in a strategic bombing offensive and in the adjoining Mediterranean and Middle East theatre.
Preceding events
Germany was defeated in World War I, and the Treaty of Versailles placed punitive conditions on the country, including significant financial reparations, the loss of territory (some only temporarily), war guilt, military weakening and limitation, and economic weakening. Germany was humiliated in front of the world and had to pay very large war reparations. Many Germans blamed their country's post-war economic collapse on the treaty's conditions and these resentments contributed to the political instability which made it possible for Adolf Hitler and his Nazi Party to come to power.
After Hitler took Germany out of the League of Nations, Mussolini of Fascist Italy and Hitler formed the Rome-Berlin axis, under a treaty known as the Pact of Steel. Later, the Empire of Japan, under the government of Hideki Tojo, would also join as an Axis power. Japan and Germany had already signed the Anti-Comintern Pact in 1936, to counter the perceived threat of the communism of the Soviet Union. Other smaller powers also later joined the Axis throughout the war.
Outbreak of war in Europe
Germany and the Soviet Union were sworn enemies, but following the Munich Agreement, which effectively handed over Czechoslovakia (a French and Soviet ally, and the only remaining presidential democracy in Central Europe) to Germany, political realities allowed the Soviet Union to sign a non-aggression pact (the Molotov–Ribbentrop Pact) including a secret clause partitioning Poland, Lithuania, Latvia, Estonia and Finland between the two spheres of influence.
Full-scale war in Europe began at dawn on 1 September 1939, when Germany used so-called Blitzkrieg tactics and military strength to invade Poland, to which both the United Kingdom and France had pledged protection and independence guarantees. On 3 September 1939, Britain and France declared war on Germany, and other allies soon followed. The British Expeditionary Force was sent to France; however, neither French nor British troops gave any significant assistance to the Poles during the entire invasion, and the German–French border, excepting the Saar Offensive, remained mostly calm. This period of the war is commonly known as the Phoney War.
On 17 September the Soviet forces joined the invasion of Poland, although remaining neutral with respect to Western powers. The Polish government evacuated the country for Romania. Poland fell within five weeks, with its last large operational units surrendering on 6 October after the Battle of Kock. As the Polish September Campaign ended, Hitler offered Britain and France peace on the basis of recognition of German European continental dominance. On 12 October the United Kingdom formally refused.
Despite the quick campaign in the east, along the Franco-German frontier the war settled into a quiet period. This relatively non-confrontational and mostly non-fighting period between the major powers lasted until Germany launched an invasion on 10 May 1940.
Germany and the USSR partition Northern Europe
Several other countries were drawn into the conflict at this time. After 28 September 1939, the Soviet government presented the governments of Estonia, Latvia and Lithuania with ultimatums threatening military invasion, thus compelling the three small nations to conclude mutual assistance pacts which gave the Soviets the right to establish military bases there. The Soviet Union issued similar demands to Finland in October 1939 but these were rejected, leading to the Soviet invasion of Finland on 30 November, starting the Winter War.