In the early years of the war Germany swept through western Europe and threatened to encircle the Mediterranean through offensives in North Africa and penetration into the Balkans. Britain, although stunned, had not been subdued. The Germans turned against their Soviet allies in the summer of 1941 and invaded the USSR, but Soviet forces stubbornly resisted the German advance. Late that year the United States entered the war on the Allied side, offering hope for the anti-Axis forces.

German and Soviet Attacks on Poland

On Sept. 1, 1939, the German military machine struck decisively at Poland, in what was known as a blitzkrieg (lightning war). High-speed panzer (tank) units pushed across the borders, blasting holes in the Polish lines. From the skies Luftwaffe (air force) bombers destroyed the Polish air force, damaged communications lines, and prevented the Poles from moving reinforcements, supplies, and ammunition to the front lines. Then German foot soldiers moved forward to hold the conquered ground. Meanwhile, Britain and France declared war on Germany on September 3.

On Sept. 17, 1939, Soviet troops marched into Poland. The Polish government and high command escaped into exile the next day. The Soviets halted at a line running from East Prussia down to the Bug River. Hitler and Stalin then partitioned the conquered country: the USSR occupied the eastern half, populated by Ukrainians and White Russians as well as Poles; the Germans took the western half, which included Gdańsk (Danzig) and the Polish Corridor.

In late September and early October, Stalin forced the Baltic States — Estonia, Latvia, and Lithuania — to accept garrisons of Soviet troops within their borders. The following year, elections held under Soviet auspices resulted in the incorporation of the three nations into the USSR as constituent republics.

Russo-Finnish War

Finland, however, resisted Soviet pressures, and on Nov. 28, 1939, the USSR denounced its nonaggression pact with that country. Two days later Red Army troops invaded Finland. The Finns put up a surprisingly spirited and at first effective resistance in this Russo-Finnish War, or Winter War. At the end of February 1940, however, the Soviets moved their best troops into battle, and the Finns began to give way to the sheer force of numbers. In March the invaders breached the defensive Mannerheim Line, and Finland was forced to relinquish strategic ports, a naval base, and airports. Meanwhile, in December 1939 the League of Nations condemned the USSR for its action in Finland and expelled it.

Struggle in the Atlantic, 1939–1940

From the very beginning of World War II, as in World War I, control of the seas was to be a critical factor in its outcome. Immediately upon the declaration of war the British Royal Navy took control of the seas and within a few weeks drove German merchant ships off the oceans into neutral ports. As in World War I the Germans replied with a methodical and destructive submarine campaign. The war was scarcely under way when a German U-boat sank (Sept. 3, 1939) the Athenia, a Canadian liner bound for Montreal. The sinking resulted in the loss of 112 lives, including those of 28 Americans. During the first 2 months of the war 67 British merchant ships were sunk. On Oct. 14, 1939, a German U-boat penetrated the defenses of Scapa Flow, the British naval base in the Orkney Islands, and sank the battleship Royal Oak; 833 lives were lost. The Germans also used long-range bombers and sea raiders.

To meet this threat the British organized a convoy system similar to that used in the late stages of World War I. Large groups of merchant ships were protected by aircraft in the early stages of their voyages and were then escorted by destroyers through the mid-Atlantic. The use of new detection devices known as radar and ASDIC, or sonar, facilitated the destruction of German surface and undersea craft. In surface warfare the British had considerable success from the beginning. The destruction of the German pocket battleship Graf Spee off Montevideo, Uruguay, on Dec. 17, 1939, was a significant blow, for the vessel had already sunk nine Allied ships. The struggle that later became known as the Battle of the Atlantic would be a long one. Not until 1943 could the Allies claim to have contained Germany's Atlantic sea power.

Denmark and Norway

After Hitler's speedy triumph in Poland, a period known as the Phony War followed in western Europe. Hitler proposed a peace conference, but the proposal was immediately rejected, and the 6-month lull was occupied with strategic planning. Hitler turned his attention to the Scandinavian peninsula, control of which would give him air bases for later attacks on Britain as well as harbors from which his rapidly increasing submarine fleet could operate in Atlantic waters. Moreover, control of Denmark and Norway would ensure the Germans a valuable source of foods such as fish and dairy products, while depriving the British of these food products. Most important of all, Norwegian routes would give Hitler access to Swedish iron ore, critical for Germany's war effort.

Early on the morning of Apr. 9, 1940, German troops swept across the Danish border. Overwhelmed and unable to resist effectively, the Danes soon capitulated. While Denmark was being overrun a German task force left Baltic ports, steamed up the Kattegat into the Skagerrak, and entered Oslo Fjord. At the same time, the Luftwaffe struck at Oslo's airport, while air transports dropped troops and guns to the ground. A parachute battalion, the first to be used in war, captured the airfield. British and French troops came to Norway's aid but succeeded only in seizing Narvik (May 28) after a month-long battle. The German conquest of Norway was completed when the Allies withdrew on June 9, 1940.

Churchill Assumes Power

Reverses in Norway caused the fall of British prime minister Neville Chamberlain, who was replaced on May 10 by Winston Churchill, a staunch opponent of appeasement in the 1930s. Before Parliament, three days later, the new prime minister offered Britons nothing but "blood, toil, tears, and sweat" in a relentless fight against Nazi Germany. Through this and many subsequent inspirational addresses, Churchill helped rally his country in Britain's darkest days against what he believed was a mortal threat to world civilization.

The Low Countries

Next on Hitler's timetable were the Netherlands, Belgium, and Luxembourg. Possession of the Low Countries would give Nazi Germany not only vast industrial resources but, more important, advance bases for coming assaults on France and Britain. An attack through the Low Countries also would divert Allied troops to the area, where they could be easily cut off. With Belgium in his hands Hitler could outflank the vaunted defensive Maginot Line, which ran parallel to the Rhine River and then north to a point near the Belgian frontier. He could then move into France across the unfortified Belgian border.

On May 10, 1940, German troops moved into the Low Countries. Luxembourg, with no defensive forces, was occupied without any resistance. Both the Dutch and Belgians fought back. Receiving the brunt of the opening offensives, the Dutch mined bridges, blocked roads, and flooded wide areas. Without sufficient planes and tanks, they relied on British and French expeditionary forces for assistance, but far too little help came and it came too late. Nazi mechanized forces moved with such speed that the Dutch were overwhelmed within 5 days. Their government, led by Queen Wilhelmina, fled to England.

The Belgians lasted only 2 weeks longer. French and British troops moved in but could not stem the German blitzkrieg. German tanks moved with great speed as parachutists dropped on the Dutch countryside and infantry troops pushed forward. To avoid further bloodshed King Leopold III ordered his troops to cease resistance and to lay down their arms in unconditional surrender on May 28, 1940.

Collapse of France

During the winter of 1939–40 the French army and the German Wehrmacht faced one another in what was regarded satirically as the sitzkrieg, or sit-down war. The world waited in anticipation of a major conflict between two powerful forces. On May 13, 1940, a bridgehead was established at Sedan, considered the gateway to France, and then suddenly, on May 16, a day after the Dutch capitulation, the German blitzkrieg was released on northern France. German mechanized forces outflanked the Maginot Line, surprised the Allies by attacking through the wooded Ardennes rather than the Belgian plain, and drove the British Expeditionary Force (BEF) from the Continent at Dunkirk (Dunkerque). On June 5 the Germans launched another offensive southward from the Somme. They entered Paris unopposed on June 14 and forced France to sign an armistice at Compiègne on June 22, 1940.

The fall of France was an extraordinary victory for Hitler. The supposedly unbeatable French army had melted away before the onslaught of his mobile units, with their convincing display of mechanized power. Nazi Germany then occupied most of France and permitted the establishment of a friendly government at Vichy, in central France on the Allier River.

The Vichy Government was headed by Marshal Henri Pétain, hero of World War I, and Pierre Laval, a collaborationist. Disgruntled French patriots rallied around Gen. Charles de Gaulle, who pronounced himself leader of the Free French.

During the early months of the war Benito Mussolini maintained Italy's neutrality. When France was about to fall he decided to join the Nazis. Declaring war on the Allies on June 10, 1940, he invaded southern France in what U.S. president Franklin D. Roosevelt described as a "stab-in-the-back."

Dunkirk Retreat

During the Belgian campaign the Germans drove rapidly across southeastern Belgium and turned toward Abbeville on the French coast, thereby isolating Allied troops. The BEF and its French comrades appeared to be doomed. While some of the troops of the French First Army sold their lives in a fierce rearguard action, from British ports sailed one of the strangest armadas in history — composed of destroyers, motor launches, private yachts, old ferries, steamers, even fishing smacks, about 850 vessels in all. While planes of the Royal Air Force (RAF) provided an umbrella over the scene to drive off German bombers, the fleet of British vessels moved to Dunkirk and proceeded to evacuate about 338,000 British, French, and Belgian troops from May 26 to June 4, 1940. Not only was a military disaster turned into a propaganda victory, but several hundred thousand experienced troops were saved for future action against the Axis.

Battle of Britain

Hitler, anticipating further eastern conquests, hoped that Britain would accept German control of the Continent and seek peace. But Britain shunned the chancellor's overtures of July 1940, and, in August, Hermann Goering's Luftwaffe began an all-out attack on British ports, airfields, and industrial centers and, finally, on London. The goal was to crush British morale and wipe out the RAF in preparation for Operation Sea Lion, an invasion of England.

The Battle of Britain was the first great air battle in history. For 57 nights London was attacked by an average force of 160 bombers. The outnumbered RAF, employing the effective Spitfire fighter and aided by radar, destroyed 1,733 aircraft while losing 915 fighters. German air power could not continue sustaining such heavy losses, and in October, Operation Sea Lion was postponed indefinitely.

The Balkans

Following the unexpected quick victory over France, Hitler turned east to the Balkans, a critical area for food and oil supplies. Penetration of this area would enable him to use overland transportation of these goods to help Germany withstand the effects of the British blockade of its shipping. Hitler moved first against Romania; in June 1940 the Soviets, who coveted Romania's substantial oil resources, had seized Bessarabia and northern Bucovina. To settle territorial disputes among the Balkan nations that might give the Soviets an opportunity for further intervention, Hitler in August ordered Romania to yield land to Bulgaria and Hungary and in September forced King Carol II of Romania to abdicate. In November, Hitler brought Romania and Hungary into the Axis alliance. At the same time, he began efforts to force Bulgaria and Yugoslavia into the Axis orbit, and this goal was achieved in 1941. Of the Balkan states only Greece remained firmly on the side of the Allies.

Mussolini, who had not been consulted on the division of Romania, decided to enhance his influence within the Axis alliance by unilaterally subjugating Greece. On Oct. 28, 1940, he began sending 200,000 troops into Greece from his puppet state Albania, expecting a speedy and overwhelming victory. Mussolini's attack was poorly planned, however, and the Greeks, although they lacked mechanized equipment and had an obsolete air force, turned on the invaders and by mid-November expelled them and penetrated into Albania.

Embarrassed by Mussolini's plight, concerned about the British troops and aircraft that had moved into the area to aid Greece, and displeased with Bulgaria's and Yugoslavia's reversion to neutralist positions, Hitler moved into the Balkans. On Apr. 6, 1941, he sent a blitzkrieg spearhead into Yugoslavia, where the pro-Nazi regime of Prince Paul had just been overthrown. The Germans struck at Belgrade and forced the surrender of the country on April 17. Simultaneously, he moved troops into Greece to smash through the defensive Metaxas Line. British forces withdrew from the Greek mainland, and by the end of the month all of mainland Greece was overrun by German forces.

The New Order

On Sept. 27, 1940, Japan was brought back into the German-Italian-Japanese grouping of the Anti-Comintern Pact, as the three nations signed a 10-year military and economic alliance, the Tripartite Pact, known as the Berlin-Rome-Tokyo Axis. Hitler regarded Japan as a buffer against the United States as well as a distraction for the USSR.

By May 1941 the Germans and their Axis allies dominated almost all of the non-Soviet European continent. Most of the territory was occupied by German troops and subject to the authority of the ruthless SS (Schutzstaffel) and Gestapo. With Europe in their grip, the Nazis proceeded to exploit its resources for the benefit of Germany regardless of the consequences for the conquered peoples. Economic wealth was pillaged for German use, and industrial plants were geared to meet German war needs. Millions of both eastern and western Europeans were sent to work in Germany's war plants in the largest forcible displacement of populations in history. Political dissidents and members of groups ranking low on the Nazi racial scale, such as Jews, Slavs, and Gypsies, were interned in concentration camps by the millions. Ultimately, at least 6 million were systematically exterminated.


The British still held the strategic island of Crete. On May 20, 1941, in a powerful display of offensive air tactics, 3,500 German paratroopers were dropped on the island. Most were killed, but a second wave of 3,000 quickly captured key defenses and overwhelmed the remaining British troops, the last of which were evacuated on May 31. Hitler now had in his possession a strategic Mediterranean island for the dispatch of reinforcements and supplies to his desert troops in North Africa, which were poised for an eastward assault against Egypt and the Suez Canal.