On 28 June 1914, Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, and his wife were assassinated by a Serbian-backed terrorist. During the crisis that followed, Europe's leaders made a series of political, diplomatic and military decisions that would turn a localised conflict in south-east Europe into a global war.

Austria-Hungary, with German encouragement, declared war on Serbia on 28 July. Russia's support of Serbia brought France into the conflict. Germany declared war on Russia on 1 August and France on 3 August. Germany's violation of Belgian neutrality and British fears of German domination in Europe brought Britain and its empire into the war on 4 August.

These actions reflect the fears, anxieties and ambitions of the European powers. The decisions for war were made in the context of growing nationalism, increased militarism, imperial rivalry and competition for power and influence. Europe's leaders were willing to go to war to defend or extend national interests and their choices were shaped by a combination of long and short-term foreign policy goals, political pressures at home, previous crises, and the system of opposing alliances that had developed over the previous 35 years.


Europe before 1914

By 1914, Europe was divided into two rival alliance systems. In 1871, German unification dramatically altered the balance of power in Europe. This new power bloc at the heart of central Europe strengthened further when Germany formed an alliance in 1879 with neighbouring Austria-Hungary, which Italy joined three years later. Fear of Germany’s growing strength encouraged Russia and France to enter into alliance in 1893. German ambitions to build a battle fleet initiated a naval arms race with Britain that seriously strained relations between the two. Britain had long seen France and Russia as potential enemies, but from 1904 it negotiated agreements with them, aiming to secure its empire by settling colonial disputes. 

The new and unlikely friendship between these three powers heightened German fears of ‘encirclement’ and deepened the divide among the European powers. Imperial rifts worsened these divisions and tensions. When Germany tried to oppose a French takeover of Morocco, Britain supported France.


A distant crisis

Relations between Austria-Hungary and neighbouring Serbia had been tense in the years before the murder of the Archduke. Austria had long seen Serbia as a threat to the stability of its multi-ethnic empire. Austria's annexation of Bosnia in 1908 and Serbian ambitions to unify south-east Europe's Slavic people further strained relations in this volatile part of Europe. Following the Balkan Wars of 1912-1913, Serbia emerged as a larger and more assertive presence in south-east Europe. On 28 June 1914, a Bosnian-Serb terrorist shot and killed Archduke Franz Ferdinand, heir to the Austrian throne. 

The assassin was 19-year-old Gavrilo Princip, one of several would-be young assassins who were intent on using violence to destroy Austria-Hungarian rule. Suspecting Serbian backing for the assassination, Austria-Hungary was determined to use the royal murder to crush the Serbian threat once and for all.


Europe takes sides

The crisis which developed in the summer of 1914 was one of several that had erupted in Europe in the early twentieth century. International tensions had been mounting, but in every previous crisis a continental war had been avoided. The assassination of Franz Ferdinand stoked old tensions beyond the Balkans. The crisis spread as other powers pledged support for either Austria or Serbia. Austria knew that conflict with Serbia would likely involve Russia, which saw itself as Serbia's protector. Austria-Hungary turned to its own ally. On 5 July, Germany promised Austria full support for a severe response against Serbia. Austria-Hungary's aggression towards Serbia and Russian support for Serbia in the aftermath of the assassination stemmed from fears that, if either backed down, they would lose credibility and prestige as great powers. 

Germany's ambitions, its perception of its own isolation and its increasing fear of 'encirclement' drove its foreign policy. The preservation of Austria-Hungary - its only reliable ally - as a great power became an important part of German policy.


Austria-Hungary declares war on Serbia

With the guarantee of German backing, Austria-Hungary issued an ultimatum on 23 July, intent on starting a war with Serbia. 

Serbia's sovereignty would be destroyed if it accepted the terms in full, but any reply other than unconditional acceptance would give Austria-Hungary its excuse for war. Austria rejected the Serbian reply, which conceded to all the ultimatum's terms except the involvement of Austro-Hungarian officials in an inquiry into the assassination. On 28 July, Austria-Hungary declared war on Serbia. It was determined to take decisive action against Serbia and, by now, knew this risked war with Russia, Serbia's supporter. Austria-Hungary was prepared to risk war because it had the guarantee of German support. The Balkan crisis now threatened a European-wide war.


Europe prepares for war

Throughout the late-nineteenth and early-twentieth centuries, Europe's leaders saw military strength as an essential part of being a great power. Britain saw its Royal Navy as its 'sword and shield'. Most of the European powers maintained mass armies through compulsory military service and embarked on large-scale arms programmes. They formulated war plans which they expected to bring swift victories if war came. But some powers were more prepared to start a war than others. 

By the summer of 1914, Germany had only one war plan, which was to knock France out of the war before turning on France's ally, Russia. German politicians saw the Balkan crisis in 1914 as an opportunity to inflict a diplomatic setback on Russia and France, but its Generals feared Russia's growing military power and were ready to strike before it was too late.


Europe goes to war

Russia ordered its forces to prepare for war on 30 July. While the Russians viewed this mobilisation as a precaution in case war broke out, the Germans saw it as an aggressive act of war directed against itself and Austria-Hungary. Germany's war plan was time-sensitive, being based upon beating France before Russia could get its army fully into action. 

On 31 July, Germany sent an ultimatum to Russia demanding it demobilise. The next day, this ultimatum expired without a reply. Germany declared war on Russia and ordered its own general mobilisation. France knew that it faced German invasion, but was clear that it must stand or fall with Russia. Many Frenchmen also hoped that war could settle old grievances with Germany stemming from the 1870s. Germany declared war on 3 August. Throughout the crisis, Russia and France were putting increased pressure on the British to declare their support. But under the terms of its agreements with Russia and France, Britain had no obligation to fight.


Britain agonises over its position

Britain was largely removed from the growing crisis in Europe until late July. News of the assassination of Franz Ferdinand was met with shock and surprise in Britain, but it was regarded as a distant crisis. As the crisis grew, British involvement remained uncertain, even as the threat of war spread across Europe. Many did not want to fight and believed that Britain should not get involved. The government was divided over Britain's involvement in what was regarded by some as a purely European affair. It had authority over the military in making final decisions for war – unlike in Germany where the military high command had immense power. Britain's foreign policy was based upon maintaining a balance of power in Europe. Britain was also determined to protect its vast global empire and its sea trade. It feared Germany's domination of the continent and its challenge to British industrial and imperial supremacy.

But until late July 1914, Britain was largely preoccupied with domestic issues. Social, industrial and political unrest and the threat of civil war in Ireland received most of the nation's attention.


Britain takes action

From 24 July, British Foreign Secretary Sir Edward Grey tried to organise an international peace conference to prevent further escalation. Although France accepted his proposals, Germany refused. On 29 July, Germany requested British neutrality in the event of a European war, which Britain refused. German victory in western Europe would establish its control along the Channel coast and pose a threat to Britain's security and trade. From 1 August, the British took further action that brought them closer to war. They mobilised the navy and promised to protect the French coast from German aggression through the Channel. On 2 August, the Cabinet agreed to support Belgium if there was a substantial violation of its neutrality.


Germany invades Belgium

German infantry crossing the Place Charles Rogier in Brussels as civilians look on following the invasion of Belgium, August 1914.
IWM (Q 88431)

After declaring war on France, Germany was now determined to execute its war plan to defeat France first and then concentrate its forces against Russia. The plan required German troops invade Belgium to get to France. This would be in direct violation of Belgium’s neutrality, which had been guaranteed in a treaty signed by major European powers, including Britain, in 1839. On the evening of 2 August 1914, Germany demanded that its troops be allowed to pass through Belgian territory. Belgium refused. Accepting Germany’s demands would make Belgium complicit in the attack on France and partially responsible for the violation of its own neutrality. 

Germany invaded on 4 August.


Britain and its Empire go to war

Germany’s invasion of Belgium tipped the balance for Britain. At 2pm on 4 August, it issued an ultimatum demanding Germany withdraw its troops. At 11pm, the deadline passed without a reply. Britain declared war. Britain’s entry into war was partially a reaction to larger anxieties about the balance of power in Europe, as well as its own security and position in the world. But by violating Belgium’s neutrality, Germany positioned itself as the belligerent aggressor and made British intervention a moral issue about the rights of small nations. The entry of Britain and its empire made this a truly global war. Europe’s leaders went to war with the general support of their citizens. This was especially important in Britain, where there was no compulsory military service and recruitment would be dependent on voluntary enlistment.

Who started the First World War?

By the summer of 1914, Europe was in a crisis. Just weeks before Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, had been assassinated in Sarajevo by a Serbian-backed terrorist. Now just a few weeks later, the continent's largest armies were mobilizing against each other with new nations joining the fight seemingly every week. The world watched with bated breath as Europe marched to war. So what happened? How did a seemingly irrelevant local conflict in southeast Europe become a World War? And why did Britain decide to get involved?

Well before we answer those questions a reminder to subscribe to the Imperial War Museums Youtube channel for more videos just like this every two weeks.

When people ask how the First World War began it's often couched in terms of a domino effect, a series of events that were almost preordained, but what I would say is that if anyone had suggested in June 1914 in Britain that World War might be about to break out and they would be met with disbelief really.

Britain hadn't fought a war on the continent since the final defeat of Napoleon at Waterloo, 99 years previously. Rather than a war in Europe, Britain was primarily occupied with its own internal affairs.

As the 20th century dawned Britain is one of the greatest powers on earth, it rules over this vast global empire. I mean it's so big that every fourth person on earth owes its allegiance to the British crown.

The Briton was the world's merchant sailor, his flag encircled the globe sixty percent of the vessels on any ocean were his.

The lifeblood of the British Empire was the sea. The Royal Navy policed the waves so that its merchant ships could trade across the globe. This brought the British Empire vast wealth, but not all of its citizens were able to share in it. Many overseas subjects were demanding greater freedom from the empire to control their own affairs, while at home domestic issues threatened to boil over.

There's this huge inequality of wealth that underpins British life at the turn of the 20th century. Only two-thirds of men have got the right to vote, absolutely no woman has the right to vote. So I'd say by the time you get to 1914 this is quite a volatile country.

The most divisive issue, however, was that of Home Rule for Ireland. Some people in Ireland wanted to be ruled from Dublin rather than Westminster, while others were bitterly opposed to this, including some vocal British politicians and a sizable contingent in the north of Ireland who considered themselves to be British. As the Home Rule Bill made its way through parliament, rival militias began to arm themselves on either side of the issue.

There is a very real threat that this is going to spill over into violence in the summer of 1914 and so to suggest to people in Britain that the conflict that's about to occur will come from Europe rather than from Ireland most people would have been very very shocked to hear that.

But while domestic tensions were rising in Britain, new tensions were coming to the fore in Europe. Germany was the new kid on the block with big ambitions. After defeating France in the Franco-Prussian war of 1870, the most powerful German state Prussia allied with smaller Germanic states to create a united Germany, but this new nation wanted an empire of its own.

Britain really initially admired this new nation, Britain really actually thought as a friend but imperial Germany soon began to threaten Britain's sense of supremacy. Its determination to up its industrial output, up its military strength, and most crucially for Britain build a rival fleet of warships.

German ships manoeuvre in the cold waters of the north sea.

This new German navy was a threat to Britain's naval dominance, the glue that held the empire together, and something for which Britain could not stand. That rivalry then turned into an arms race as each nation tried to outproduce the other with ever greater feats of technology. This culminated in the production of Dreadnought battleships which were seen as the nuclear weapons of their day.

That factor means Britain's now started to see Germany as a threat, by the time you get to say 1907 Europe's really split into two opposing camps.

Germany had disturbed the delicate balance of power in Europe. France, fearing this new empire on their doorstep, allied with Russia in the east. An unlikely friendship for two of Europe's most ideologically opposed nations. That then left Germany feeling surrounded and pushed them to form an alliance with the Austro-Hungarian Empire and to a lesser extent Italy. Finally, Britain and its empire, afraid of German domination on the continent, drifted closer to France and Russia, though without going as far as forming an alliance.

You've got Germany Austria-Hungary and Italy and you've got France Russia and to some extent Britain. There's still no immediate reason for war between the two, it would take a crisis to turn tensions into an armed conflict.

And that crisis came in the summer of 1914. The Balkans in Southeast Europe had been a hotbed of unrest for some time, with two wars in the preceding three years. Those wars had made Austria-Hungary's neighbour Serbia much larger, prompting tensions between the two nations to rise even further. When Archduke Franz Ferdinand was assassinated in June by a Serbian-backed terrorist, Austria-Hungary felt it had no choice but to assert its dominance.

Austria-Hungary sets out to punish Serbia it wants to quash support for Serbian nationalism. It's encouraged by its ally Germany. So after Serbia failed to meet the terms of a very draconian ultimatum Austria-Hungary declares war on Serbia and this act of war this stirs up these old tensions and anxieties right across the continent because it draws in supporters and allies on both sides.

When Austria-Hungary declared war on Serbia Russia came in to back the Serbs in defence of a fellow Slavic nation. When Germany, in support of its ally, then declared war on Russia that brought France into the war on Russia's side. Italy however did not join the war, as its alliance with Germany and Austria-Hungary was a defensive pact. In a matter of weeks then Europe's largest powers were primed for war, but Britain was still in two minds over whether it should be involved.

It agonized over whether to support Russia and France. I think at the heart of Britain's anxieties it came down really to Britain fearing German domination of Europe because if a victorious but hostile Germany dominated the continent and threatened Britain's position in the world that was just intolerable for Britain.

The tipping point came thanks to Germany's war plans. Hoping to defeat France quickly before Russia had a chance to mobilize her forces, Germany attempted to skirt around the French defences in Alsace-Lorraine by attacking through neutral Belgium, a country Britain had sworn to protect.

On the 4th of August Britain issues an ultimatum to Germany which is ignored, which ends in Britain declaring war on Germany and by Britain declaring war on Germany that also means its global empire is at war and you have a conflict set up that becomes very rapidly a world war.

The causes of the First World War are complex, they're still debated to this day. The nations didn't realize it at the time, but their attempts to defend what they perceived as their own national interests created a war that would shape Europe for decades to come. Most participants expected the war to be over by Christmas, but as we know the reality was very different.

The First World War became what we would call a total war. These nations pitted against each other, millions of men fighting on land, on the sea, in the air, modern weaponry causing mass casualties and ultimately the war broke the empires of Germany, of Russia, Austria-Hungary, it forced the USA onto the world stage and the war also laid the seeds for future conflict in places like the Middle East. So it ultimately defined the shape of Europe and the world in the 20th century and this is how it all began.

Related Content

An interwar Earl Haig Fund 'Remembrance Day' poppy
© IWM (EPH 2313)
First World War

Why We Wear Poppies On Remembrance Day

The poppy is the enduring symbol of remembrance of the First World War. It is strongly linked with Armistice Day (11 November), but the poppy's origin as a popular symbol of remembrance lies in the landscapes of the First World War.

A group of 'Leeds Pals' at their training camp in the Yorkshire Dales shortly after enlisting in September 1914.
First World War

From Civilian To First World War Soldier In 8 Steps

After the outbreak of war in August 1914, Britain recruited a huge volunteer citizens' army. In just eight weeks, over three-quarters of a million men in Britain had joined up. Every volunteer had to undergo a series of medical and fitness tests before being accepted as a soldier. 

This is the moment of resolution for the Peace Conference when the leading allied politicians are able to demonstrate their determination and unity as the treaty is signed, as well their political power. The setting is the dazzling Hall of Mirrors at Versailles, built by Louis XIV, at vast expense as a demonstration of his political power.
© IWM (Art.IWM ART 2856)
First World War

The Peace Treaties That Ended The First World War

On 11 November 1918, an armistice came into effect ending the war in Western Europe – but this did not mean the return of peace. The armistice was effectively a German surrender, as its conditions ended any possibility of Germany continuing the war. 

IWM Shop

Gift range
First World War

Explore our online shop for products inspired by people's experience of conflict.

While there is tea there is hope mug

This retro style enamel mug bears a mantra always worth keeping in mind, 'While there is tea there is hope'.

Distressed leather backpack

This distressed leather backpack is inspired by the kit bags that were carried by soldiers during the First World War. It is made from 100% real buffalo leather, with distressed finish and the strap can be changed to be worn over body or as a backpack.