PARIS, France - On the eve of World War I, Europe's great powers ruled the globe, their scientists, engineers and artists at the peak of innovation. Yet in 1914, the Old Continent plunged into a war of unprecedented violence, dragging half the planet in its wake.
The Great War of 1914-18 sucked in nations from every continent, with battles fought around the globe. But its roots were firmly in Europe.
"Like all its predecessors, it began as a purely European conflict, arising out of the conflicting ambitions and mutual fears of the European powers," explained British historian Michael Howard.
From the Urals to the Atlantic, these powers - Britain, France, Germany, Austria-Hungary, Russia and the Ottoman Empire - were in many ways unchanged since the 18th century.
Many were even ruled by the same centuries-old dynasties: Kaiser Wilhelm II in Germany, George V of Britain and Russia's Tsar Nicolas II were cousins.
But the European continent, whose 450 million people made up nearly a third of the world population, was also living through a time of unsettling change as the industrial revolution transformed largely agrarian societies.
By the turn of the 20th century, the imperial powers Germany, France and Britain together accounted for more than a third of world industrial output, although the United States was the largest single economy.
Competition was fierce between the rival empires as they jostled for political, military and commercial supremacy.
Germany was openly seeking to challenge the Royal Navy's mastery of the seas - a source of concern for British leaders - and to increase its colonial empire, feeding tensions with both Britain and France.
In Europe's south, Russia and the Austro-Hungarian Empire were vying for control of the Balkans, where the influence of the Ottoman Empire was waning.
It was here in the Balkans that the preamble to the Great War was played out, as two conflicts tore through the region between October 1912 and early 1913.
Serbia, backed by Bulgaria, Greece and Montenegro, formed a "Balkan League" that successfully wrested control from the Turks of their remaining European possessions - only to go to war again amongst themselves over the spoils.
With the exception of Russia - allied with Serbia in the name of pan-Slav solidarity - Europe's great powers stood back as these Balkan crises unfolded.
But Serbia's population was doubled as a result, and its ambitions to "liberate" Serbs living under Austrian rule greatly encouraged.
'Encircled by enemies'
Meanwhile, Europe's powers had one by one bound themselves into two rival alliances - the "Triple Alliance" of Germany, Austria-Hungary and Italy, and the "Triple Entente" of France, Britain and Russia.
This state of affairs left the continent's greatest power - Imperial Germany - feeling encircled by enemies, France and Britain to the West and Russia to the east.
For Berlin and its militaristic ruler Wilhelm II, the unfolding power play in the Balkans was seen as weakening its Austrian partner, and reinforcing Serbia's ally Russia.
Europe's powers had been at war on-and-off for centuries leading up to 1914 and Germany's military leaders believed it was only a matter of time before the next European war.
In that spirit, Germany in 1913 expanded its armed forces by 300,000 men, prompting France to extend compulsory military service to three years.
In both camps, "the mood was one of nationalism, as well as a great deal of anxiety, a fear of being outmanoeuvred by the other side," summed up the German historian Gerd Krumeich.
But beyond German leadership circles, as the French historian Nicolas Offenstadt stresses, there was little sense of war being inevitable.
"There were tensions on some levels, but also the ability to solve crises," he argued.
Pacifism was strong across the continent, and even as the prospect of war reared its head, there was none of the unanimous support that was to emerge once the conflict began.
At the outset of 1914 the mood in Europe was, on the surface of things, peaceful.
But with the great powers bound into complex treaties of mutual assistance, the continent was a tinderbox primed to explode.
No turning back
The spark, as generations have been taught, was provided by the assassination on June 28 in Sarajevo of Archduke Franz-Ferdinand, heir to the Austrian throne, by a teenaged Serbian nationalist named Gavrilo Princip.
Until the last moment, Europe's leaders thought they could avoid - as they had done with the recent Balkan wars - being sucked into the conflict.
That was without counting on a series of errors of judgement that set the continent irrevocably on the path to war.
Austria struck against the Serbs in a bid to restore its authority in the Balkans. It was encouraged to do so by Germany - which bet that its powerful rival Britain would stay out of any European conflict that ensued.
Russia ordered the mobilisation of its armed forces, hoping to intimidate Austria and protect its Serbian ally. Instead it prompted its French ally to mobilise in turn - and provided the justification for Germany to do the same.
From that point, as long-set German war plans heaved into motion, there was no turning back.
On August 3, Germany declared war on both France and Serbia, and sent its troops marching through neutral Belgium towards the French border.
Britain declared war on Germany the following day, honouring the terms of a defence treaty with Belgium.
Over the following 52 months, the Great War dragged almost half the world's population into a war that historians have described as "suicidal" in scale and intensity.
It left some 10 million dead and 20 million injured and maimed on battlefields that sprawled from the howling North Sea coast to the deserts of the Middle East.
Millions of civilians perished under occupation, through massacres, disease, hunger or deportation.
Four of the world's most powerful empires - Russian, German, Austro-Hungarian and Ottoman - collapsed as the world map was redrawn.
And Europe's economic and political ruin cleared the way for the rise of a new superpower, the United States.