Introduction

World War I, brought to a close by the Armistice of 11 November 1918, had resulted in over 20 million deaths, an astonishing, heretofore unseen number. The “Great War” indeed, it easily surpassed the largest wars fought in Europe until then: the Thirty Years’ War of the seventeenth century and the Napoleonic Wars of the nineteenth century. The countries that experienced the war contemplated carefully the steps they could take so as to never again endure a war of this magnitude. These included introducing a system of collective security with the Treaty of Versailles (the League of Nations’ Covenant) and the Locarno Treaties; enacting the Pact of Paris outlawing war (Kellogg-Briand Pact); and holding international conferences for the purpose of disarmament. A mere 21 years later, however, World War II started on September 1, 1939.

One of the major causes of World War II was the establishment of the regime of Adolf Hitler in Germany with its pursuit of a policy of foreign expansionism. British historian A.J.P. Taylor, arguing the counterpoint in The Origins of the Second World War, pointed out the role that British and French passivity played in inciting German arrogance. The debate over the war’s causes has been lively ever since. Arguably, the personalities of the British, French, German, Italian, and Soviet leaders had brought on the war. In addition to these factors, it may be necessary to look at such issues as the domestic political situations in each country, the international system of the time, and international conditions outside of Europe, as well. In this chapter, I shall present a general overview of the origins of World War II in Europe, seasoned with some insights on these other issues.

Post-WWI International System

The balance of power policies of every country in Europe were thought to be a cause of World War I. US President Woodrow Wilson called for the formation of a general association of nations (League of Nations), a concept of building collective security arrangements, in his “Fourteen Points” address outlining principles for world peace. The Treaty of Versailles, which put collective security in writing, and the Pact of Paris (1928), which outlawed wars of aggression, provided the basic rules for this system.

The postwar peace in Europe was built upon the scapegoating of Germany, one of the defeated Central Powers in the war. Germany was obliged to pay 132 billion gold marks in reparations (in the 1921 London schedule of payments), an enormous sum that the country was still paying off in the twenty-first century. In addition, it lost 40,000 square kilometers of territory and seven million of its population. In the 1925 Locarno Treaties, its western border zone with France and Belgium was demilitarized and the signatories pledged to treat it as inviolable. Such measures sought to restrain Germany by force, but the collective security arrangements and legal aspects to support those measures were left extremely ambiguous.

First of all, the collective security system, logically being between major powers and their potential adversaries, had difficulty functioning; absent any strong compulsion, states found it hard to intervene in a conflict in a region lacking any connection to their own national interests. Although Article 16 of the League of Nations’ Covenant clearly states that any member disregarding the League’s covenants will be “deemed to have committed an act of war” and will immediately be subject to sanctions, it had a fatal flaw, in that each member had the right of refusal, so there was no obligation to sanction or use military force against an aggressor. The fact that a key country, the United States, did not join the League meant that this system was in a precarious state right from its foundation.

In addition, the Kellogg-Briand Pact, by failing to provide a clear definition of a war of aggression, was interpreted to permit only wars of self-defense. But it held almost no validity as a treaty and, as international legal scholar Shinobu Junpei pointed out, “the Pact, far from outlawing war, was an endorsement legitimating the conduct of war in general” (Shinobu 1941). There was a nagging feeling, even in those days, that idealism had gotten too far ahead of the institutions that shaped postwar international relations, as suggested by a remark Winston Churchill made in a speech: “The League shall never replace the Grand Fleet.” That is, the international institutions of the interwar period were not set up to deal with countries that did not abide by the system or take the solidarity and cooperation of its member countries seriously, nor were they designed to suppress with force countries that attempted to destroy the system using force.

There was an idea, however, to limit each country’s military strength through a variety of disarmament conferences. Article 8 of the League of Nations’ Covenant obligates members of the League to reduce national armaments, with the League itself to play an important role in providing a venue for multilateral discussions on the matter.

Disarmament Conferences: Successes and Setbacks

Relatively many international conferences on disarmament were held in the interwar years. The characteristic of disarmament conferences of this period is that the humanitarian argument for the complete abolishment of poison gas and bomber aircraft as inhumane weapons existed alongside the strategic argument that reducing naval vessels and ground warfare armaments possessed by all countries would decrease the possibility of war. Of the two, strategic arms limitations made relatively more progress.

The Washington Naval Conference (1921–1922) and the First and Second London Naval Conferences (1930, 1935–1936), for instance, all concluded with treaties signed, whereas the Geneva Naval Conference (1927) and the Geneva Conference for the Reduction and Limitation of Armaments (1932–1933) did not. Perhaps the most successful was the Washington Naval Conference, which brought together the five sea powers of the era (Britain, the United States, Japan, France, and Italy) to avoid a naval arms race in vessel construction by setting quantitative limits on both aircraft carriers and battleships. The Washington Conference established a broader framework for international cooperative security called the Washington System, one aspect of which was naval disarmament.

As the Great Depression that started in October 1929 in the United States reverberated worldwide, governments turned to measures serving their own national interests, rather than to international cooperation, to overcome the crisis. Countries with many colonies, such as Britain and France, aimed to protect their national industries and currency by solidifying their own economic bloc, leaving Japan and Germany to suffer considerable economic damage. Amid such conditions, the Manchurian Incident occurred September 18, 1931, an event the Japanese public supported enthusiastically. The Imperial Japanese Army (IJA) carried out the Manchurian Incident from a national security perspective, to resolve the Manchuria question, but the incident ultimately harmed Japan’s international standing. Britain appeared willing to come to terms with Japan in the League of Nations but, facing opposition from League members on the issue of recognizing Manchukuo, Japan announced March 27, 1933 that it would be withdrawing from the League.

Nevertheless, the British government held out a sliver of hope for the Second London Naval Treaty Conference scheduled for 1935. But the preliminary and exploratory talks in 1934 broke off, with the United States locked in competition with Japan, each rebutting the other’s assertions, and the US pursuit of idealistic calls for arms reduction in total opposition to Britain’s push for realistic limits.

Japanese Ambassador to the United States Saitō Hiroshi formally notified Secretary of State Cordell Hull of Japan’s intent to terminate the Washington Naval Treaty in the afternoon of December 29, 1934 (Washington time). As the treaty would cease to be in force 2 years following such notification, Japan had arranged for the date to coincide with the timing of the London Naval Treaty’s expiration at the end of 1936. On March 25, 1936, Britain, the United States, and France signed the Second London Naval Treaty, its key features being the mutual notification of naval vessel construction plans and the setting of qualitative limits on vessels. Despite being asked, Japan refused to join.

The absence of treaties in the naval arena meant that a future naval construction arms race was inevitable after 1936. Starting in fiscal year 1937, the Imperial Japanese Navy (IJN) implemented a massive naval buildup around plans to construct the battleships Yamato and Musashi under the Third Naval Armaments Supplement Program (maru-san). As if to counter this, the US government enacted the Naval Act of 1938 in May of that year (the Second Vinson Act) that mandated a 20% increase in strength of the US Navy. The British government, too, commenced plans for a large-scale buildup over 1936–1939, setting the Royal Navy’s strength at the level of the combined naval strengths of Japan and Germany, and constructing seven battleships, four aircraft carriers, and 20 cruisers. Thus, one wing of the interwar international order, the Washington System, was crumbling, and the naval arms race that everyone had feared had come to pass.

The Geneva Conference on the topic of European disarmament opened in February 1932. It convened 62 countries from around the world to discuss limits on all offensive weapons, land, naval, and air. Two points of interest were the debate over whether to regard tanks, submarines, and bombers as offensive weapons, and thus restrict their use, and whether France, Europe’s largest land and air power, would actively take arms reductions measures. Using the League of Nations’ Covenant to its advantage, Germany, then subject to the severest limitations on military armaments, argued that every country, and not only Germany, must face an equal set of restrictions, a position that France completely disagreed with.

Germany’s potential national power, though reduced by the Treaty of Versailles’ arms limitations, far surpassed that of France. In contrast to France whose lands became World War I battlefields, Germany saw its industrial belt survive the war largely unscathed; the German population was also 20 million larger than France’s. In addition, France arguably needed to maintain the Versailles system and keep suppressing Germany for the sake of its own national security, as France owed a sizable debt to the United States and Britain. The issue was whether Germany would continue to consent to that state of affairs.

Supposing France were to permit Germany to rearm, Paris would require a security guarantee from London. The French government planned to take no measures on arms reductions without a firm commitment for assistance from Britain. Yet, the Ramsay MacDonald government remained uninterested in the issue of disarmament and French national security. The British government’s attitude during this period did not encompass a spirit of international cooperation.

The unenthusiastic attitude of Britain and France toward arms reduction and limitation gave Germany the excuse it needed to insist on a principle of equality in armament. In protest, Germany pulled out of the Geneva Conference in October 1933 and withdrew from the League of Nations, as well. Early that year, Adolf Hitler had become the German chancellor on January 30, and his government was secretly moving ahead with a military expansion program. The Führer’s aims were vast: to isolate France in Western Europe and thereby destroy the Versailles system, and to expand the German military in order to acquire Lebensraum in the east. So, naturally, the British and French postures against disarmament in Geneva provided Germany with an excuse to rearm. Germany declared its intent to rearm on March 16, 1935, tripling the strength of the army and building a new Luftwaffe at a stroke. Anticipating the true threat from German rearmament, the British government had already approved Expansion Scheme A in July 1934 to build up the Royal Air Force (RAF).

The years 1933–1934 might be characterized as the turning point of the interwar period. Idealism seeking international cooperation and peace was in retreat; realism, and the turn toward military expansion to establish one’s own national security, was on the rise. Not every country reacted this way to conditions during this period. British Prime Minister MacDonald and French Prime Minister Aristide Briand had to pursue their realistic policies amid a general domestic trend of idealism, which complicated the issues. It was said that British members of parliament, reacting to the report on the RAF extension scheme, could be heard asking as to the purpose of the military buildup.

A Crisis of Diplomacy

Britain, France, and Italy issued the final declaration of the Stresa Conference in April 1935, affirming a tripartite coalition in opposition to Germany’s declaration to rearm. To defend against German expansion in eastern Europe, Paris also concluded the Franco-Soviet Treaty of Mutual Assistance with Moscow on May 2, 1935. These moves were of the old tradition, measures to maintain the balance of power by relying on separate alliances, rather than through a system of collective security as stipulated in the Locarno Treaties. However, a coalition among Britain, France, Italy, and the Soviet Union should have had enough power to restrain Germany. A just 2 months after its declaration, however, the Stresa Front abruptly collapsed because the British government separately concluded the Anglo-German Naval Agreement. It was the start of Britain’s appeasement policy to Germany.

Meanwhile, Italian Duce Benito Mussolini announced the invasion of Ethiopia on October 2. The League of Nations responded by imposing economic sanctions against Italy; they were faltering half-measures from the start. Mussolini warned Britain and France that their participation in applying economic sanctions would bring about war with Italy. The two countries, foreseeing a confrontation in Europe with Germany, did not welcome making Italy an adversary over some distant country in Africa; they even devised the Hoare-Laval plan, attempting to provide justification for Italy’s aggressive actions. When newspapers reported on the plan in December, the British public erupted in anger, forcing Foreign Secretary Samuel Hoare to resign. Despite urgent entreaties from the Ethiopians, the League of Nations took no action. This is the moment when the League’s collective security system fell apart.

Exploiting the disorder stirred up by the Ethiopia question, Germany boldly moved to occupy the Rhineland on March 7, 1936, abrogating the Locarno Treaties that had designated that area as a demilitarized zone. France had two options to respond: take a firm stance militarily or pursue a peaceful policy diplomatically. Confronted with an unequivocal act of aggression, France could have exercised its right of self-defense militarily under the terms of the Locarno Treaties, without waiting for League of Nations’ arbitration. The day following Germany’s occupation, French Foreign Minister Pierre-Étienne Flandin requested the French military to deploy some army units, but Army Chief of Staff Maurice Gamelin, fixated on defensive operations along the Maginot Line, did not accede to his request. If Britain and France had cooperated at this stage, even if it meant war, they just might have been able to crush the German army. Decision makers and the public opinions of both countries continued to shy away from resolute action that might lead to war. British Prime Minister Stanley Baldwin remained indifferent to the French position, saying that the German move was not act of aggression. Since it was dangerous for France to act alone without a firm British commitment of assistance, Paris ultimately chose the option to avoid confronting Germany directly.

A.J.P. Taylor summarized this French response to the Rhineland Occupation: “… they closed their eyes to it and pretended that it did not exist.” (Taylor 1961, p. 114) Furthermore, the Popular Front cabinet of French Prime Minister Léon Blum prioritized domestic economic sanctions over diplomacy. France was unable to take decisive policies against Germany because its national power was in decline during this period (weakening economy, decreasing birthrate) and the political situation was unstable.

France’s actions made its neighbors uneasy. Belgium decided to withdraw from its military accord with France and declare itself neutral. The governments of the eastern European parties to the French-leaning Little Entente (Czechoslovakia, Romania, Yugoslavia) indicated their disillusionment with Paris’ attitude. Even Moscow abandoned Franco-Soviet cooperation, turning instead to a Berlin-leaning diplomacy and concluding the German–Soviet Trade and Credit Agreement (1939). France, for the most part, became isolated in Europe. Britain, the ally France should have been able to depend on, had only just started to increase the strength of its army, so going to war with Germany was not yet feasible. “No one then breathed about [German] sanctions,” wrote British Under-Secretary of State for Foreign Affairs Robert Vansittart about contemporary conditions. “The Labour Party indeed expressly repudiated them. Our obligation, had said Sir Herbert Samuel for the Liberals, was ‘not to arm but disarm.’ The Conservative majority sat tight” (Vansittart 1943, p. 53). A League of Nations Council meeting was held in London on March 14, 1936; although the Council did recognize that the German occupation of the Rhineland was a violation of the Treaty of Versailles, it ultimately was unable to take any action whatsoever.

All too quickly, Hitler achieved his objective of dismantling the system established by the Versailles and Locarno treaties. His adversaries, Britain and France, sought to win over Italy as a stopgap measure to give themselves time to rearm. On July 4, 1936, both governments lifted the economic sanctions that they had imposed related to Ethiopia, hoping to improve ties with Italy. But Germany acted first. With the outbreak of the Spanish Civil War in July, Germany and Italy backed the regime of Generalissimo Francisco Franco, and the two announced the creation of a Rome-Berlin axis on October 25. Britain and France had been outmaneuvered once again. British Prime Minister Neville Chamberlain, naturally alarmed, wanted to make friendly approaches to Italy regardless of how it looked; disagreeing, his Foreign Secretary Anthony Eden resigned.

Britain was confronted with a thornier challenge when the Second Sino-Japanese War erupted on July 7, 1937. Even though the Japanese government had hammered out a strategy to simultaneously advance north on the continent and south into the South Seas under its Fundamentals of National Policy of August 7, 1936, it would be more fitting to say the Second Sino-Japanese War was the result of chance overlapping with opportunism, instead of design. The Japanese-German Anti-Comintern Pact concluded November 25, 1936 began to link the situations in Europe and East Asia.

Much like the situation France faced in Europe, the British in East Asia did not have the means to oppose Japan alone, without US support. Since the League of Nations still seemed dysfunctional, Britain did what it could, persistently engaging Japan in negotiations and giving itself more time by providing China with assistance. The Guomindang government did not want the situation in Europe to deteriorate further, having concluded that Britain and the Soviet Union would seek to appease Japan if it did. Preparing for the worst, the premier of the Republic of China, Chiang Kai-shek began to consider forging closer ties to the United States. Each of these countries had no choice but to proceed while carefully observing the situations in both Europe and East Asia.

The Outbreak of World War II

Germany’s annexation of Austria on March 13, 1938 (Anschluss) gave greater clarity to the shape of Italo-German ties. Italy originally opposed the annexation of Austria, but Mussolini gave his consent. Hitler’s next target was the Sudetenland in Czechoslovakia. Formerly a part of the Austro-Hungarian Empire, it had been annexed by Czechoslovakia after World War I despite having three million German-speaking inhabitants, some of whom started a campaign seeking self-determination. Czechoslovakia, for its part, signed a mutual assistance treaty with France in 1924 that obligated Paris to provide military assistance for Czechoslovakia’s defense in the case of a German military invasion. The problem in practice, however, was that Germany already had so surpassed France in terms of air power that France was could not to defend itself in a time of national crisis.

Here too, Britain’s attitude and approach was the key. Chamberlain was not enthusiastic about defending Czechoslovakia; on the point of self-determination of ethnic groups, he appeared to show understanding for Germany. The French government briefly considered a policy of countering Germany by including the Soviet Union, which had signed its own mutual assistance pact with Czechoslovakia. But, given the British government’s deep-rooted mistrust of the Soviet Union, Franco-Soviet discussions did not even commence.

In this context, the Munich Conference opened on September 29, 1939. Participants included Hitler, Chamberlain, and French Prime Minister Édouard Daladier; Italian Duce Mussolini moderated. Representatives of Czechoslovakia and the Soviet Union were not even invited to the conference. Chamberlain pressed ahead with an appeasement policy toward Hitler, acknowledging German claims for the cession of the Sudetenland. For Chamberlain, defending Czechoslovakia was unrealistic and British public opinion would not allow the option of waging total war against Germany for that purpose. The British people felt a deep aversion to war notwithstanding their domestic preparations such as air raid shelters readied against German bombs and distribution of poison gas masks. Even Daladier, initially sympathetic to the Czechoslovaks, simply followed Chamberlain’s lead in Munich.

Criticizing Chamberlain and Daladier for their policy of appeasement has a touch of judging in hindsight quality to it. Contemporary public opinion welcomed the British and French politicians for both seeking to avoid war, a position that had public backing, and then achieving that goal. The German people, too, fêted them as heroes. Even US President Franklin D. Roosevelt praised the outcome for a time.

The outcome of the Munich Conference, however, caused a major shift in the situation in Europe. Distrustful of Britain and France, the Soviet Union drew closer to Germany in order to establish its own security arrangements. Hitler became convinced that Britain and France would try to avoid war, no matter the sacrifice. He soon aimed to seize the whole country of Czechoslovakia not just the Sudetenland, but before that he set his sights on Poland.

The basic concept with Poland closely resembled the issue with the Sudetenland. Germany undertook negotiations with Poland over returning the Free City of Danzig, where most inhabitants were of German descent, but talks broke down on March 26, 1939. Unlike with Czechoslovakia, the plans of Britain and France did not include compromise. Were Germany to take possession of Danzig, it would stabilize its eastern border and enable it to obtain strategic natural resources from the region. Therefore, Britain and France both regarded the issue of Poland as one that might cause troubles for them later. The Franco-Polish mutual assistance treaty of 1921 obligated France to come to Poland’s aid. Britain preferred to join with Poland rather than the Soviet Union. The British government had engaged the Soviet Union in talks of a military alliance throughout April and May of 1939, but after failing to get any meaningful results, concluded a mutual assistance treaty with Poland on August 24, 1939, preparing together with France for a German invasion of Poland. It remained unclear how the two countries would defend Poland, however.

The Soviet Union, meanwhile, rapidly drew closer to Germany. The two had been engaged in secret talks that came to fruition on August 23 with the Soviet-German treaty of non-aggression (Molotov–Ribbentrop Pact). Having thus secured its rear, Germany carried out a sudden invasion of Poland on September 1. Two days later, Britain and France declared war on Germany in accord with their mutual assistance pacts with Poland. The Soviet Union, on the basis of the secret protocol to its non-aggression pact with Germany, attacked Poland from the east on September 17. Thus, World War II began.

In Conclusion

E.H. Carr, a British historian and former diplomat, tried to glean lessons from international relations in Europe in the interwar years. In The Twenty Years’ Crisis, Carr argued with a sense of urgency that moralistic utopianism was being superseded by authoritarian realism. Following the Occupation of the Rhineland, however, British and French compliance with German demands, Carr argued, was based on their understanding that Germany’s demands followed a certain logic, rather than to hold off the crisis. In other words, that the Treaty of Versailles, which formed the foundation of European international security system in the interwar period, was itself unreasonable for Germany. Nevertheless, the Hitler regime cannot shirk its responsibility for the war by blaming structural problems in international relations.

We also tend to overlook the issue of time. So quickly did the chain of events unfold in the latter half of the 1930s, it is hard to say that countries had enough time for analysis and consideration. France, antagonistic to Germany throughout the interwar period, tried to overcome this confrontation through a policy of allying with several countries, but there had not been time enough to build relationships of trust and so they all were hastily assembled. According to American international relations scholar Stephen Walt, an alliance requires a certain amount of time before it can function properly, time to build a relationship of trust and to institutionalize the alliance. So, looking at developments from 1935 to 1939, you might say there was not nearly enough time for that.

During that interval, the sole constant is that Hitler’s Germany always moved before other countries could act, leaving Britain and France continually outmaneuvered. Democracies clearly need time for politicians to reach concensus amongst themselves and to make policies that take public opinion into consideration. Japan, too, concluded an alliance with Germany and Italy, feeling as if it was about to “miss the bus.” However, like Hitler, who for a time seemed to be doing quite well, both saw their grand strategies end in failure by making adversaries ultimately of the United States and the Soviet Union, both.

Bibliography: For Further Reading

Shinobu, Junpei. 1941. Senji kokusaihō kōgi, dai-1kan (Lectures on International Law in Wartime, Volume 1). Tokyo: Maruzen.

Taylor, A.J.P. Yoshida, Teruo (trans). 2011. Dai-niji sekai taisen no kigen (The Origins of the Second World War). Tokyo: Kōdansha Gakujutsu Bunko. [Originally published as: Taylor, A.J.P. 1961. The Origins of the Second World War. New York: Simon & Schuster Paperbacks.]

A book on the topic of the origins of World War II that caused a stir. While there are some objections to the book, the content is suitable as a general statement.

Vansittart, Baron Robert Gilbert. 1943. Lessons of my Life, by the Rt. Hon. Lord Vansittart. London: Hutchinson.

Additional Bibliography

Carr, Edward Hallett. Hara, Yoshihisa (trans). 2011. Kiki no nijūnen: risō to genjitsu (The Twenty Years’ Crisis: The Ideal and the Reality). Tokyo: Iwanami Bunkō. [Originally published as: Carr, E.H. 1946. The Twenty Years’ Crisis, 1919–1939: an Introduction to the Study of International Relations: by E.H. Carr. London: Macmillan.]

A consideration of European international relations in the interwar period, it is also renowned as an international political science textbook. There are two translations, an old and new; the newer one is easy to read.

Murray, Williamson; Knox, MacGregor; and Bernstein, Alvin (eds). Ishizu, Tomoyuki; Nagasue, Satoshi (trans). 2007. Senryaku no keisei: shihaisha kokka sensō. gekan (The Making of Strategy: Rulers, States, and War [Last Volume]). Tokyo: Chūō Kōron Shinsha. [Originally published as: Murray, Williamson; Knox, MacGregor; Bernstein, Alvin (eds). 2009. The Making of Strategy: Rulers, States, and War. Cambridge: Cambridge University Press.]

The British, US, French, German, and Soviet military strategies in the interwar period are written about in detail from various standpoints.

Nye, Joseph S., Jr.; Welch, David A.; Tanaka, Akihiko; and Murata, Kōji (trans). 2013. Kokusai funsō: risō to rekishi (International Conflict: Theory and History). Tokyo: Yūhikaku. [Originally published as: Nye, Joseph S., Jr.; Welch, David A. 2013. Understanding Global Conflict and Cooperation: an Introduction to Theory and History (Ninth Edition). Boston: Pearson.]

A textbook for international security studies, its fourth chapter is a detailed commentary on the international politics of the interwar years.

Ōi, Takashi. 2008. Ōshū no kokusai kankei 1919–1946: furansu gaikō no shikaku kara [European International Relations, 1919–1946—from the angle of French Diplomacy] Tokyo: Tachibana Shuppan.

Very knowledgeable on French diplomatic policies of the interwar period.