It has been called the "seminal catastrophe" of modern times and the calamity from which all other calamities sprang.
In fact, you have to wonder if, in all of history, more tears have flowed over anything quite so much as they did over the First World War and all of its tragic consequences.
The conflict itself saw 16 million killed, including 10 million soldiers, half of whom, it has been estimated, were never found or identified in the sea of mud and craters that the battlefields became.
No one will ever be able to calculate the lifetimes of grief left for those millions of relatives of the fallen, and for those survivors with broken bodies and spirits.
For years after the war, people talked of "the great silence" as the pain lay too deep to be spoken aloud.
Those of my generation were familiar with seeing the visible survivors, men in their late 60s and older without arms or legs, sometimes with only half their faces, and so many with damaged minds.
On another level of regret, the war's societal devastation seeded so many deadly political consequences.
In just four years it collapsed four entire empires — the German, the Austro-Hungarian, the Russian, and the Ottoman (Turkish).
It bankrupted Europe both literally and emotionally, shattered faith in governments everywhere and left people desperate for extreme new ideologies that promised to make life livable again.
By giving birth to communism, fascism and the Nazis, the First World War was the essential precondition for the Second World War just 21 years later, and for the nuclear age and Cold War that followed.
"It is hard to imagine a worse initial condition for the modern era of which we are the inheritors," the Australian historian Christopher Clark wrote.
Still feeling its tremors
Indeed, to this day shockwaves from that monster war continue to rumble through our world.
Its aftershocks, it can be argued, broke up the WW I-created Yugoslavia in the 1990s, as its key nationalities found they couldn't live as one.
Similar shockwaves have kept much of the Middle East dangerously aflame in intractable clashes that owe their genesis to the aftermath of 1918.
After the Turkish Ottoman Empire collapsed, Britain and France redrew most of the frontiers of the Middle East, and the names so often linked to today's crises — Syria, Lebanon, Iraq and Iran, the Gulf region, North Africa — are largely the creations of that postwar diplomacy.
And of course the ceaseless Israel-Palestinian crisis can be traced to WW I British promises of land to both sides, promises that inevitably came into conflict.
Even the renewed tension in Eastern Europe today links back to the First World War peace treaties, which promised Ukraine an autonomy that was then snatched away in the early 1920s by the new Soviet Union.
To quote the title of a new book by British sociologist Frank Furedi on the centenary of the 1914 conflagration: First World War: Still No End in Sight.
A reckless dance
The war even embittered the new superpower of the 20th century, the United States. Late to arrive, it still lost 116,000 dead in less than 10 months.
The ensuing disillusion led the U.S. into an aloofness that seriously weakened Europe's democracies and effectively destroyed the fledgling League of Nations, its failure another stage-setter for the Second World War.
Canada was one of the few countries to feel itself to have gained, becoming through its sacrifice a recognized sovereign country "forged in fire."
Our small population, barely a quarter of today's, lost an appalling 60,000 dead. But historians confirm our battle honours were clearly seen as a defining national moment that tends to be remembered with enormous pride.
In Europe the scale of the casualties could not support such positive views.
Despite thousands of ceremonies and monuments to comfort civilians, the numbers lost defied comprehension — 700,000 from Britain were killed, nearly 1.4 million from France.
I first toured our battlefield cemeteries in France and Belgium in my youth over a half-century ago, and can still feel, in the new histories coming out, that war's continuing power to shock and sadden.
I never expected to be quite so moved again, but I have felt increasingly caught up in the poignancy of those memories while helping plan the 1914-18 "In Memoriam" ceremony at the University of Toronto's Varsity Stadium tomorrow (Thursday), which is intended to mark the last dying hours of peace on July 31, 1914, before the "guns of August" took over.
Throughout that July a century ago, the public warnings of war that followed the Austrian archduke's assassination grew remarkably slowly until they reached a torrent in the final 10 days.
The speed was dizzying. There was far too little time to negotiate, almost no open debate and only limited public comment.
The obvious need for an emergency summit of the leading nations was never seriously acknowledged.
Even the top levels of governments, the history books now reveal, seem barely informed of the deadly dance of diplomats and generals.
Most striking to me was the innocence of the European public. Because the great powers had avoided large wars for decades, people certainly did not expect, or seek, a giant "world war" that would go on for months let alone years.
But though ordinary Europeans (and Canadians) had not wished for conflict, people appeared to come around remarkably quickly to support their own nation's claim that they were fighting a purely defensive war.
Over its four years, the First World War came to be seen as a battle of existence, an encompassing struggle over culture and values that made compromise impossible.
Soldiers and civilians alike came to hope that so much sacrifice in blood would ensure a singular legacy for future generations by making their awful ordeal a "war to end all wars."
Sadly it was anything but. Still we honour the noble wish, at least, and the astounding bravery of those days.
What we should never forget is the real legacy of that war, which is to stand as the greatest warning ever against the sheer folly of reckless and accidental conflicts that have no obvious end.
Europe and the Middle East: Changes from 1914 to the present
Swipe from right to left on each map to see how the political borders have changed.
THE MIDDLE EAST