Causes of World War II

Moving Towards Conflict

Photos Benito Mussolini & Adolf Hitler riding together in a car, 1940

National Archives & Records Administration

Many of the seeds of World War II in Europe were sown by the Treaty of Versailles that ended World War I. In its final form, the treaty placed full blame for the war on Germany and Austria-Hungary, as well as exacted harsh financial reparations and led to territorial dismemberment. For the German people, who had believed that the armistice had been agreed to based on US President Woodrow Wilson's lenient Fourteen Points, the treaty caused resentment and a deep mistrust of their new government, the Weimar Republic. The need to pay war reparations, coupled with the instability of the government, contributed to massive hyperinflation which crippled the German economy. This situation was made worse by the onset of the Great Depression.

In addition to the economic ramifications of the treaty, Germany was required to demilitarize the Rhineland and had severe limitations placed on the size of its military, including the abolishment of its air force. Territorially, Germany was stripped of its colonies and forfeited land for the formation of the country of Poland. To ensure that Germany would not expand, the treaty forbade the annexation of Austria, Poland, and Czechoslovakia.

Rise of Fascism and the Nazi Party

In 1922, Benito Mussolini and the Fascist Party rose to power in Italy. Believing in a strong central government and strict control of industry and the people, Fascism was a reaction to the perceived failure of free market economics and a deep fear of communism. Highly militaristic, Fascism also was driven by a sense of belligerent nationalism that encouraged conflict as a means of social improvement. By dismantling existing political structures, approximately between 1925 and 1927, Mussolini was able to make himself the dictator of Italy and transformed the country into a police state. By the mid-1930s, Italy was explicitly a totalitarian, one-party, fascist state, as laid out in writings by Mussolini himself.

To the north in Germany, Fascism was embraced by the National Socialist German Workers Party, also known as the Nazis. Swiftly rising to power in the late 1920s, the Nazis and their charismatic leader, Adolf Hitler, followed the central tenets of Fascism while also advocating for the racial purity of the German people and additional German Lebensraum (living space). Playing on the economic distress in Weimar Germany and backed by their "Brown Shirts" militia, the Nazis became a political force. On January 30, 1933, Hitler was placed in a position to take power when he was appointed Reich Chancellor by President Paul von Hindenburg

The Nazis Assume Power

A month after Hitler assumed the Chancellorship, the Reichstag building burned. Blaming the fire on the Communist Party of Germany, Hitler used the incident as an excuse to ban those political parties that opposed Nazi policies. On March 23, 1933, the Nazis essentially took control of the government by passing the Enabling Acts. Meant to be an emergency measure, the acts gave the cabinet (and Hitler) the power to pass legislation without the approval of the Reichstag. Hitler next moved to consolidate his power and executed a purge of the party (The Night of the Long Knives) to eliminate those who could threaten his position. With his internal foes in check, Hitler began the persecution of those who were deemed racial enemies of the state. In September 1935, he passed the Nuremburg Laws which stripped Jews of their citizenship and forbade marriage or sexual relations between a Jew and an "Aryan." Three years later the first pogrom began (Night of Broken Glass) in which over one hundred Jews were killed and 30,000 arrested and sent to concentration camps.

Germany Remilitarizes

On March 16, 1935, in clear violation of the Treaty of Versailles, Hitler ordered the remilitarization of Germany, including the reactivation of the Luftwaffe (air force). As the German army grew through conscription, the other European powers voiced minimal protest as they were more concerned with enforcing the economic aspects of the treaty. In a move that tacitly endorsed Hitler's violation of the treaty, Great Britain signed the Anglo-German Naval Agreement in 1935, which allowed Germany to build a fleet one third the size of the Royal Navy and ended British naval operations in the Baltic.

Two years after beginning the expansion of the military, Hitler further violated the treaty by ordering the reoccupation of the Rhineland by the German Army. Proceeding cautiously, Hitler issued orders that the German troops should withdrawal if the French intervened. Not wanting to become involved in another major war, Britain and France avoided intervening and sought a resolution, with little success, through the League of Nations. After the war several German officers indicated that if the reoccupation of the Rhineland had been opposed, it would have meant the end of Hitler's regime.

The Anschluss

Emboldened by Great Britain and France's reaction to the Rhineland, Hitler began to move forward with a plan to unite all German-speaking peoples under one "Greater German" regime. Again operating in violation of the Treaty of Versailles, Hitler made overtures regarding the annexation of Austria. While these were generally rebuffed by the government in Vienna, Hitler was able to orchestrate a coup by the Austrian Nazi Party on March 11, 1938, one day before a planned plebiscite on the issue. The next day, German troops crossed the border to enforce the Anschluss (annexation). A month later the Nazis held a plebiscite on the issue and received 99.73% of the vote. International reaction was again mild, with Great Britain and France issuing protests, but still showing that they were unwilling to take military action.

The Munich Conference

With Austria in his grasp, Hitler turned towards the ethnically German Sudetenland region of Czechoslovakia. Since its formation at the end of World War I, Czechoslovakia had been wary of possible German advances. To counter this, they had built an elaborate system of fortifications throughout the mountains of the Sudetenland to block any incursion and formed military alliances with France and the Soviet Union. In 1938, Hitler began supporting paramilitary activity and extremist violence in the Sudetenland. Following Czechoslovakia's declaration of martial law in the region, Germany immediately demanded that the land be turned over to them.

In response, Great Britain and France mobilized their armies for the first time since World War I. As Europe moved towards war, Mussolini suggested a conference to discuss the future of Czechoslovakia. This was agreed to and the meeting opened in September 1938, at Munich. In the negotiations, Great Britain and France, led by Prime Minister Neville Chamberlain and President Édouard Daladier respectively, followed a policy of appeasement and caved to Hitler's demands in order to avoid war. Signed on September 30, 1938, the Munich Agreement turned over the Sudetenland to Germany in exchange for Germany's promise to make no additional territorial demands.

The Czechs, who had not been invited to conference, were forced to accept the agreement and were warned that if they failed to comply, they would be responsible for any war that resulted. By signing the agreement, the French defaulted on their treaty obligations to Czechoslovakia. Returning to England, Chamberlain claimed to have achieved "peace for our time." The following March, German troops broke the agreement and seized the remainder of Czechoslovakia. Shortly thereafter, Germany entered into a military alliance with Mussolini's Italy.

The Molotov-Ribbentrop Pact

Angered by what he saw as the Western Powers colluding to give Czechoslovakia to Hitler, Josef Stalin worried that a similar thing could occur with the Soviet Union. Though wary, Stalin entered into talks with Britain and France regarding a potential alliance. In the summer of 1939, with the talks stalling, the Soviets began discussions with Nazi Germany regarding the creation of a non-aggression pact. The final document, the Molotov-Ribbentrop Pact, was signed on August 23, and called for the sale of food and oil to Germany and mutual non-aggression. Also included in the pact were secret clauses dividing Eastern Europe into spheres of influence as well as plans for the partition of Poland.

The Invasion of Poland

Since World War I, tensions had existed between Germany and Poland regarding the free city of Danzig and the "Polish Corridor." The latter was a narrow strip of land reaching north to Danzig which provided Poland with access to the sea and separated the province of East Prussia from the rest of Germany. In an effort to resolve these issues and gain Lebensraum for the German people, Hitler began planning the invasion of Poland. Formed after World War I, Poland's army was relatively weak and ill-equipped compared to Germany. To aid in its defense, Poland had formed military alliances with Great Britain and France.

Massing their armies along the Polish border, the Germans staged a fake Polish attack on August 31, 1939. Using this as a pretext for war, German forces flooded across the border the next day. On September 3, Great Britain and France issued an ultimatum to Germany to end the fighting. When no reply was received, both nations declared war.

In Poland, German troops executed a blitzkrieg (lightning war) assault combining armor and mechanized infantry. This was supported from above by the Luftwaffe, which had gained experience fighting with the fascist Nationalists during the Spanish Civil War (1936-1939). The Poles attempted to counterattack but were defeated at the Battle of Bzura (Sept. 9-19). As the fighting was ending at Bzura, the Soviets, acting on the terms of the Molotov-Ribbentrop Pact, invaded from the east. Under assault from two directions, the Polish defenses crumbled with only isolated cities and areas offering prolonged resistance. By October 1, the country had been completely overrun with some Polish units escaping to Hungary and Romania. During the campaign, Great Britain and France, who were both slow to mobilize, provided little support to their ally.

With the conquest of Poland, the Germans implemented Operation Tannenberg which called for the arrest, detainment, and execution of 61,000 Polish activists, former officers, actors, and intelligentsia. By the end of September, special units known as Einsatzgruppen had killed over 20,000 Poles. In the east, the Soviets also committed numerous atrocities, including the murder of prisoners of war, as they advanced. The following year, the Soviets executed between 15,000-22,000 Polish POWs and citizens in the Katyn Forest on Stalin's orders.

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Hickman, Kennedy. "Causes of World War II." ThoughtCo, Apr. 5, 2023, thoughtco.com/world-war-ii-road-to-war-2361456. Hickman, Kennedy. (2023, April 5). Causes of World War II. Retrieved from https://www.thoughtco.com/world-war-ii-road-to-war-2361456 Hickman, Kennedy. "Causes of World War II." ThoughtCo. https://www.thoughtco.com/world-war-ii-road-to-war-2361456 (accessed March 19, 2024).