World War II (1939–1945): The Start of the War

The Soviet Invasion of Poland

Just two weeks after the German invasion began, Soviet troops invaded Poland from the east, on September 17, 1939. It took them only two days to push far enough to meet German troops advancing from the west. By this time, Germany had already taken most of Poland except for Warsaw, which was under siege. Upon meeting the Russian troops, the Germans handed over large numbers of prisoners and promptly pulled back to the line agreed upon in the German-Soviet Nonaggression Pact. Retreating Polish armies, unaware that the USSR was part of Germany’s occupation plan, fled directly into Russian hands.

Allied Declarations of War and the “Sitzkrieg”

Britain and France—which were soon labeled the Allied Powers, just as they had been in World War I—both declared war on Germany on September 3, 1939, just two days after Germany began its invasion of Poland. However, aside from basic defensive preparations, neither country took significant action for several months. Rather, Britain initiated a propaganda effort against Hitler by using its bombers to drop millions of anti-Nazi leaflets over Germany. Among the British public, this effort soon came to be known as the “confetti war.”

Germany likewise took little action after the invasion of Poland was complete, aside from several small naval attacks on Allied shipping vessels. This period of relative calm has been sarcastically labeled the “Sitzkrieg,” or sitting war—a play on blitzkrieg. Rather than make an offensive move of their own, the Allies waited for the expected German attack on Belgium and France. It would not come for many months, until the late spring of 1940.

The Russo-Finnish War

The one active hot spot during this “Sitzkrieg” was Finland, which the USSR invaded on November 30, 1939, with the goal of seizing the eastern Finnish territory of Karelia. Though vastly outnumbered and outgunned, the Finns fought back with determination and innovation, even employing troops on bicycles and skis. The invasion, which was expected to end quickly, instead lasted until March 13, 1940, when Finland finally capitulated, ceding Karelia to the Soviet Union, along with the major port of Viipuri (present-day Vyborg). Although Finland lost territory, the victory cost the USSR more than 200,000 lives, more than twice the number that it cost the Finns.

Denmark and Norway

After months of inaction, the first sign that Hitler was again on the move came in early April 1940. On April 9, German troops simultaneously took Copenhagen, the capital of Denmark, and landed on the coast of Norway. Denmark gave in almost immediately. In Norway, although the capital at Oslo was quickly taken and a puppet government set up, a strong resistance movement supported by Britain and France continued to fight the Germans for two months. The combat was generally limited to the less densely populated areas in the north of the country.