11m people died to improve our lives.
T was supposed to be "the war to end all wars." It wasn't, and we're still living with the consequences.
IBritain should have stayed out of the Great War, and our intervention was "the biggest error in modern history" says historian Niall Ferguson.
Rival narrator Max Hastings admits that the conflict was "a colossal calamity for mankind" but insists it "wasn't futile".
"If the Kaiser's Germany had triumphed," he argues "the consequences would have been grievous not only for the British Empire but for freedom and democracy in Europe."
The sides was At home, entire young " As with lawyers, so with historians. You pays your money and you takes your choice.
World War One ended with the Armistice that we commemorate on the 11th hour of the 11th day of November, which in this centenary year falls on Remembrance Sunday. The guns finally fell silent after four years of carnage, but not so the voices demanding - if not "a land fit for heroes" - then something better than the one they went to fight for.
The terrible down side of WW1 was of course the loss of human life. 700,000 Britons killed, rising to almost a million with Empire casualties.
Nearly two million Germans died in combat, and the overall death toll including civilians exceeded 11 million. Nothing on this scale had occurred in history before.
suffering on all unspeakable. it felt like an generation of men had been lost.
The suffering on all sides was unspeakable. At home, it felt like an entire generation of young men had been lost. Ex-servicemen begging on the streets were a common sight.
But climacteric events have upsides, too. The war hastened votes for women, who had left home and hearth to work in munitions factories, on the railways and in supporting military roles. They were not to be silenced.
It also gave impetus to a social revolution, moving Britain away from a deferential culture towards egalitarianism. No more sending daughters to skivvy in "the big house".
And it accelerated political change, bringing the Labour Party into government, short-lived though it was, within five years. The landscape of power was redefined. These radical reforms were not what the Establishment had in mind when the nation declared war after the assassination of Archduke Franz Ferdinand of Austria in faraway Sarajevo.
But they were the beneficial outcome of such a cataclysm. Like money, war changes everything, though not always forever.
Only 20 years after British soldiers were demobbed, they were recalled to fight the old enemy, then under new management headed by Herr Hitler.
At least the historians agree that was a just war, and like WW1 it ushered in social progress: Universal secondary education, the NHS and the welfare state.
What a pity it takes such horrors to improve our lives.
The suffering on all sides was unspeakable. At home, it felt like an entire generation of young men had been lost.