While the assassination of Archduke Franz Ferdinand in Sarajevo is a key event often cited as the cause of World War I, it was less a cause and more a spark that ignited a pre-existing tinderbox of imperial rivalries, economic competition, and intricate military alliances.

The war was the culmination of decades of tension between the great European powers, who were all vying for global dominance and control over territories and resources.

The Underlying Imperialism and Economic Competition

The late 19th and early 20th centuries were an era of intense globalization, driven by a new wave of imperialism. The major European powers—Britain, France, Germany, and Russia—were locked in a ruthless competition for colonies in Africa and Asia. These colonies were not just symbols of national prestige; they were vital sources of raw materials and new markets for the industrial goods of the metropole.

• Britain’s Global Empire: At the turn of the century, the British Empire was the largest in the world, covering a quarter of the globe and controlling key shipping lanes and resources. This vast empire was a source of immense wealth and power, but it also made Britain deeply protective and suspicious of any rival that threatened its dominance.

• Germany’s "Place in the Sun": Newly unified in 1871, Germany felt it had arrived late to the colonial party. Under Kaiser Wilhelm II, the country aggressively pursued its own "place in the sun," seeking to build a global empire to match its economic and military might. This ambition directly challenged Britain's naval supremacy and its colonial holdings. This was a core rivalry that fueled the arms race.

• The Scramble for Africa: The Berlin Conference of 1884-1885 had carved up Africa for European powers, but it did little to resolve the underlying tensions. The Agadir Crisis of 1911 is a prime example of this. When Germany sent a warship to Morocco to challenge France's influence there, it nearly triggered a war. While the conflict was averted, it highlighted the intense imperial rivalries that simmered just beneath the surface, proving that even a small piece of African territory could be a flashpoint for a major European war.

These colonial rivalries were fundamentally economic. Britain, with its massive overseas markets and raw material sources, was wary of Germany's rapidly growing industrial output. Germany’s industrial production had surpassed Britain's by 1914, and it sought to use its economic power to gain political and military leverage on the global stage. This economic competition directly translated into military expansion.

The Arms Race and Military Alliances

As imperial and economic tensions mounted, European nations entered into a dangerous cycle of military buildup. The most significant was the naval race between Britain and Germany. Britain, dependent on its navy to protect its global trade routes and its empire, saw Germany's ambitious naval expansion as a direct existential threat. Germany’s construction of a modern fleet of battleships, including the new and powerful Dreadnought class, forced Britain to divert immense resources to keep its naval advantage. The arms race was not just a defensive measure; it was an offensive one, a visible sign that these countries were preparing for a large-scale war.

This arms race was reinforced by a complex and rigid system of military alliances. These alliances were meant to be a deterrent, but they had the opposite effect, creating a "domino effect" that meant a small regional conflict could quickly spiral out of control.

• The Triple Entente: This alliance, solidified by 1907, consisted of France, Russia, and Britain. It was a response to the growing power of the Central Powers and was meant to provide a collective security against a potential German attack.

• The Triple Alliance: This alliance, formed in 1882, consisted of Germany, Austria-Hungary, and Italy. Italy, however, was a reluctant partner and would later switch sides.

This system of alliances meant that the assassination of Franz Ferdinand was not just a conflict between Austria-Hungary and Serbia. Because Austria-Hungary declared war on Serbia, Russia, as Serbia's protector, mobilized its forces. This triggered Germany, as Austria-Hungary’s ally, to declare war on Russia and its ally, France. Finally, when Germany invaded neutral Belgium to attack France, Britain, which had a treaty to protect Belgium, was pulled into the conflict.

The Domino Effect of a Single Act

The assassination of Archduke Franz Ferdinand on June 28, 1914, was indeed the trigger. It gave Austria-Hungary the pretext it needed to settle a long-standing grievance with Serbia, which it saw as a hotbed of anti-Austrian nationalism. Austria-Hungary issued a harsh ultimatum to Serbia, knowing that Serbia could not fully comply. Serbia's partial refusal was all the justification Austria-Hungary needed to declare war.

However, if these underlying tensions had not existed—if Britain and Germany weren't locked in a naval arms race, if Russia hadn't felt the need to protect a Slavic nation in the Balkans, if France hadn't been an ally of Russia, and if all of Europe weren't on a knife's edge of imperial rivalry—the assassination would have likely remained a regional incident. Instead, it was the spark that set off a century of accumulated imperial rivalry and military buildup.

The story of World War I is, at its core, a story of empires clashing. The war was the final, tragic outcome of a world where nations saw global dominance as a zero-sum game, where economic competition and colonial ambitions led to a military arms race, and where a rigid alliance system ensured that no one could back down once the first domino fell.