The causes of the Second World War are neither singular or straightforward. This section will explore the primary causes which led to the outbreak of war in 1939.
Germany’s foreign policy
Germany’s aggressive foreign policy was not the sole cause of the Second World War, but it was a large contributing factor.
From 1935 onwards, Germany had actively pursued an aggressive foreign policy: reintroducing conscription, creating the Luftwaffe, planning for war as detailed in the Hossbach Memorandum of 1937, and occupying Austria, the Sudetenland, and Czechoslovakia before eventually invading Poland in 1939.
By breaking international agreements set out in the Treaty of Versailles and pursuing aggressive expansionism, Germany’s actions made a major European war more likely.
The aftermath of the First World War
Following the end of the First World War, the Treaty of Versailles was agreed. Whilst a temporary economic recovery appeared between 1924-1929, Germany remained politically and economically fragile.
The Wall Street Crash in 1929 once again decimated the economy, and the resulting economic instability created political instability. The political instability from 1929-1933 led to disillusionment with politics and a rise in support for extremist parties such as the Nazis.
The Treaty of Versailles also reduced the size of Germany. This had numerous outcomes, among them losing key economic outputs, as well as making people who had previously been German part of other countries. The change in the eastern borders of Germany in particular became a source of contention, and as a result many people within Germany felt that the treaty was unfair. This again led to discontent and was exploited by extremist parties such as the Nazis who rejected of the treaty.
Weakness of the International System and the Policy of Appeasement
Whilst Germany’s foreign policy played a decisive role in the outbreak of the Second World War, the failure of other countries to react, or their inability to react, was also key.
The aftermath of the First World War had also left France and Britain in politically and economically weak situations. This meant that they were often unwilling or unable to respond effectively to German aggression.
Britain in particular felt that the Treaty of Versailles, and its effects on Germany, were harsh. Following the devastation of the First World War, Britain was desperate to avoid another world war. As a result of this followed a policy of appeasement towards Hitler’s aggressive foreign policy from 1933-1939. This policy boosted Hitler’s confidence and as a result his actions became progressively more bold.
Outside of mainland Europe, the USA and the Soviet Union also played key roles in the outbreak of the Second World War. In the lead up to 1939, both countries followed increasingly isolationist policies, keeping themselves out of international foreign affairs where possible.
The USA had not joined the League of Nations, and had passed several Neutrality Acts in 1938 which avoided financial and political war-related deals.
As a major power, the USA’s reluctance to involve itself in other countries affairs helped to embolden Hitler and the Nazis. This contributed to the rise of Nazism in Europe, and its confidence to carry out its aggressive foreign policy without fear of retaliation from the USA.
In addition to this, following the Nazi-Soviet Pact of 1939 , the Soviets ceased to be an immediate threat to the Nazis. This allowed them to start the war for Lebensraum with Soviet support.
When combined, these factors reduced the chances of an effective challenge to Nazi Germany preceding the Second World War. It meant that Hitler was able to get progressively more confident without fear of retaliation or serious action from other powers.
Creation of the Axis Powers
Throughout the 1930s, new alliances were forged across Europe.
The Spanish Civil War [1936-1939] helped to unite Italy and Germany, who both offered military support to the nationalist rebels attacking the democratic government. Prior to this, Italy and Germany had not been militarily aligned, and Italy had blocked Germany’s plans to annex Austria in 1934.
Following the Spanish Civil War however, relations between the two countries improved. In October 1936, the Rome-Berlin Treaty between Italy and Germany was signed.
The following month in November 1936, an anti-communist treaty, the Anti-Comintern Pact, was signed between Japan and Germany. In 1937, Italy joined this pact.
The three countries formalised these pacts into a military alliance in 1940. The countries that were part of this alliance became known as the Axis Powers. When coupled with Germany’s aggressive foreign policy, the creation of an alternative military alliance to the Allies, intensified the volatile situation.
The failure of the Allied Powers in summer 1939
The Soviet Union and Nazi Germany were ideological enemies. Despite this, the Soviet Union and Nazi Germany entered into a non-aggression pact in the summer of 1939, which allowed them to invade and occupy parts of Poland. This pact suited both countries territorial aims.
This situation however, was not inevitable. In 1939, the Soviet Union was initially engaged in talks with the Allies over a defensive strategy for Poland. When these talks broke down, the Soviet Union turned back towards Germany, quickly agreeing the Molotov-Ribbentrop Pact.
Ultimately, the Allies failed to make a concerted effort to work together to prevent Hitler’s attack on Poland. This failure was a contributing factor in the outbreak of the Second World War.