How did WWI start?
The simplest answer is that the immediate cause was the assassination of Franz Ferdinand, the archduke of Austria-Hungary. His death at the hands of Gavrilo Princip – a Serbian nationalist with ties to the secretive military group known as the Black Hand – propelled the major European military powers towards war.
The events that led up to the assassination are significantly more complicated, but most scholars agree that the gradual emergence of a group of alliances between major powers was partly to blame for the descent into war.
By 1914, those alliances resulted in the six major powers of Europe coalescing into two broad groups: Britain, France and Russia formed the Triple Entente, while Germany, Austria-Hungary and Italy comprised the Triple Alliance.
As these countries came to each other's aid after the assassination of Franz Ferdinand, their declarations of war produced a domino effect. CNN lists these key developments:
June 28, 1914 - Gavrilo Princip assassinates Franz Ferdinand.
July 28, 1914 - Austria-Hungary declares war on Serbia.
August 2, 1914 - Ottoman Empire (Turkey) and Germany sign a secret treaty of alliance.
August 3, 1914 - Germany declares war on France.
August 4, 1914 - Germany invades Belgium, leading Britain to declare war on Germany.
August 10, 1914 - Austria-Hungary invades Russia.
As the war progressed, further acts of aggression drew other countries, including the United States, into the conflict. Many others, including Australia, India and most African colonies, fought at the behest of their imperial rulers.
But even the alliance theory is now considered overly simplistic by many historians. War came to Europe not by accident, but by design, argues military historian Gary Sheffield.
According to Sheffield, the First World War began for two fundamental reasons: "First, decision-makers in Berlin and Vienna chose to pursue a course that they hoped would bring about significant political advantages even if...