Explore the causes of the First World War, from the political and military developments of the late nineteenth century to the international crises and decisions that led to war in 1914.
Causes of the First World War
The First World War was caused by a combination of long-term tensions and immediate events. Nationalism, imperial rivalry, alliances and militarism increased tensions between the European powers, while instability in the Balkans and a series of international crises made relations increasingly difficult. In 1914, the assassination of Archduke Franz Ferdinand triggered a crisis that developed into a European war.
The outbreak of war was therefore the result of several interconnected developments rather than a single cause. Understanding why war broke out requires consideration of both the long-term changes in European politics and the decisions made during the crisis of July 1914.
The Road to War
The causes of the First World War can be traced through a series of political, military and diplomatic developments stretching back several decades. The Franco-Prussian War of 1870–71, the creation of a unified Germany, the development of competing alliance systems, imperial rivalries, military expansion and the instability of the Balkans all contributed to the international situation that existed in 1914.
Nationalism
Nationalism was an important force in European politics before 1914. The growth of national identities and demands for national independence challenged existing political arrangements, particularly in areas where different national groups lived within large empires.
Nationalism was especially significant in the Balkans. Serbia and other newly independent states sought to establish and extend their independence, while Austria-Hungary was concerned about nationalist movements among the peoples within its own empire.
Nationalist ambitions therefore created tensions both between states and within multinational empires. In the Balkans, nationalism became closely connected with the rivalry between Austria-Hungary, Russia and the emerging states of south-eastern Europe.
Imperial Rivalry
The major European powers competed for territory, influence and economic opportunities overseas. The expansion of European empires created rivalries that affected relationships between the powers.
Germany’s emergence as a major industrial and military power altered the existing balance of power. German ambitions overseas brought it into competition with established imperial powers, while disputes such as the Moroccan Crises demonstrated how imperial disagreements could become wider diplomatic confrontations.
Imperial rivalry did not make war inevitable, but it contributed to the atmosphere of competition and suspicion that existed between the European powers before 1914.
Alliances and Power Blocs
The European powers developed increasingly complex networks of alliances and agreements during the decades before the war. These arrangements were intended to provide security, but they also contributed to fears of encirclement and made the consequences of an international crisis potentially much greater.
Germany developed a close relationship with Austria-Hungary and was also associated with Italy through the Triple Alliance. France sought security through its relationship with Russia, while Britain developed increasingly close diplomatic relations with France and Russia, resulting in the Triple Entente.
The alliance system did not cause the war by itself. Its importance was that a dispute involving one country could draw other major powers into the crisis.
Militarism and the Arms Race
Military power became increasingly important to European governments before 1914. The major powers expanded their armed forces, invested in new weapons and developed detailed plans for mobilisation and war.
The growth of military power affected political thinking. Governments increasingly had to consider the military consequences of diplomatic decisions, while military leaders developed plans based upon assumptions about the speed with which opponents could mobilise.
Anglo-German Rivalry and the Naval Race
Relations between Britain and Germany were particularly affected by competition over naval power. Britain had long regarded naval superiority as essential to the security of its islands and its worldwide empire.
Germany’s naval expansion challenged Britain’s established position. The construction of modern battleships, including the British Dreadnought, contributed to an arms race that increased suspicion between the two countries.
The naval race did not cause the First World War on its own, but it formed part of the wider rivalry between Britain and Germany.
The Balkans and the Decline of the Ottoman Empire
The weakening and disintegration of Ottoman power created instability in south-eastern Europe. As Ottoman authority declined, different states and nationalist movements competed for territory and influence.
Austria-Hungary wanted to protect its position in the region, while Russia sought greater influence in the Balkans and supported Slavic interests. Serbia also emerged as an increasingly important regional power.
The Balkan Wars of 1912–13 further destabilised the region. They demonstrated the strength of competing national ambitions and increased the possibility that another Balkan crisis could involve the major European powers.
Why Did Tensions Become So Dangerous by 1914?
The existence of alliances, military preparations and international rivalries did not automatically lead to a general European war. Earlier crises had been resolved without producing a continent-wide conflict.
What made 1914 different was the combination of several circumstances. European governments faced domestic political pressures, diplomatic communications were imperfect, military mobilisation plans placed increasing pressure on decision-makers, and the Balkans remained highly unstable.
Domestic Political Pressures
Domestic politics formed part of the context in which governments responded to the international crisis. Britain was dealing with major political disputes over Irish Home Rule, the women’s suffrage movement and industrial unrest.
Other European governments also faced significant domestic pressures. These did not cause the First World War in isolation, but they affected the circumstances in which governments assessed the developing crisis.
Diplomacy, Communications and Timing
The final crisis developed with extraordinary speed. Governments, ambassadors and military authorities depended heavily on telegraph communications and diplomatic messages, while mobilisation schedules increasingly restricted the time available for political decisions.
Communication difficulties and the timing of diplomatic decisions could therefore have significant consequences. Messages could be delayed, misunderstood or overtaken by events as governments moved towards mobilisation.
The limited time available during the July Crisis made the search for a diplomatic settlement increasingly difficult.
The Assassination of Franz Ferdinand
On 28 June 1914, Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, and his wife Sophie were assassinated in Sarajevo by Gavrilo Princip.
The assassination was the immediate trigger for the crisis that followed, but it did not by itself cause a European war. The importance of the assassination lies in the decisions that followed: Austria-Hungary’s response to Serbia, German support for Austria-Hungary, the Serbian response, Russian mobilisation and the subsequent decisions of the other European powers.
Read more about the Assassination of Franz Ferdinand
The July Crisis
Following the assassination, Austria-Hungary sought German support before confronting Serbia. Germany gave its backing, and Austria-Hungary subsequently issued Serbia with an ultimatum on 23 July 1914.
Serbia accepted most of the demands but rejected or qualified some of them. Austria-Hungary declared war on Serbia on 28 July.
The crisis then widened rapidly. Russia began mobilisation in support of Serbia. Germany declared war on Russia and France, and German military action against Belgium brought Britain into the conflict.
The July Crisis was therefore the point at which the long-term tensions of European politics were converted into a rapidly developing military conflict.
Read more about the Outbreak of the First World War
The Schlieffen Plan and German Military Planning
Military planning became increasingly important once mobilisation began. Germany had prepared for the possibility of a war against France and Russia, with the Schlieffen Plan providing the basis for German planning for a war on two fronts.
The Schlieffen Plan was not a long-term cause of the tensions that produced the war. Its importance lies in what happened once the crisis developed. German military planning placed pressure on the timing of mobilisation and contributed to the decision to move German forces through Belgium.
The German invasion of Belgium brought Britain directly into the European conflict and helped transform the crisis between Austria-Hungary and Serbia into a much wider war.
Read more about the Schlieffen Plan
Why Did a Balkan Crisis Become a European War?
The assassination of Franz Ferdinand was therefore a trigger rather than a complete explanation for the First World War.
By 1914, Europe was divided by competing alliances, military rivalries and political tensions. Nationalism and imperial competition had contributed to instability, while the Balkans had become an area of particularly intense conflict between national movements and the interests of the major powers.
The decisions taken after the assassination turned this existing instability into a general crisis. Austria-Hungary’s decision to attack Serbia, German support for Austria-Hungary, Russian mobilisation, German declarations of war and the invasion of Belgium progressively widened the conflict.
From European War to World War
The conflict quickly extended beyond the original dispute. The European powers possessed global empires, overseas territories, trade networks and military forces around the world.
As a result, the war involved territories and forces far beyond Europe from its early stages. The wider international dimensions of the conflict are explored in The First World War as a Global Conflict.
Why Did the First World War Happen?
The First World War resulted from the interaction of long-term and short-term causes. Nationalism, imperial rivalry, alliances and militarism created a tense international environment, while Anglo-German rivalry, the arms race and instability in the Balkans increased the potential for conflict.
These factors did not make a general war inevitable. The decisive transformation came in 1914, when the assassination of Franz Ferdinand produced a crisis that governments failed to contain. Austria-Hungary’s confrontation with Serbia, German support, Russian mobilisation, military planning and the decisions taken during the July Crisis transformed a regional dispute into a European war.
The causes of the First World War must therefore be understood as a combination of the conditions that made Europe unstable and the decisions that turned the crisis of 1914 into war.
Further Reading
- Hew Strachan, The origins of the First World War, International Affairs, 90:2 (2014), pp. 429–439.
- Annika Mombauer, July Crisis 1914, 1914-1918-online: International Encyclopedia of the First World War (2017).
- The Outbreak of the First World War, UK Parliament — a collection of contemporary documents and images relating to the European crisis and outbreak of war.