Now we associate the Great War with gut-wrenching horror. But the first painting to truly depict it was immediately censored.

What you notice first about the two figures in Christopher Nevinson's painting Paths of Glory is the banality of their death. Their commonplace, mundane fate. They lie face down in the blasted earth, two men in British military fatigues, their helmets and rifles lying in the mud beside them.

They are indistinguishable from each other, stripped of individual identity. Nothing marks them out as the unique human beings they must once have been with names, and families, and remembered childhoods, and desire and love and hope and ambition.

From the bottom left of the composition, where the corpse in the foreground lies with the soles of his boots facing you, your eye moves diagonally upwards and to the right, to the second dead man, who has fallen forwards towards you, and you see the top of his dark head but Nevinson denies you a glimpse of his face. He has no face, no personality, no story of his own. In colour, texture and even contour, the lifeless bodies are almost indistinguishable from the land on which they lie, and which will now swallow them.

The picture the censors didn't like Allan Little discusses how government censors did not like Paths of Glory - an image of two anonymous dead boys in the mud of the Western Front - because it was judged bad for morale. Listen to The Essay: Minds At War on BBC Radio 3 on Monday 23 June at 22:45 BST. Or catch up on iPlayer

In my time as a war reporter for the BBC I have come across scenes like this. You cannot mistake the recently dead for the sleeping, for there is something bloodless, something shockingly, arrestingly lifeless about them. I have found myself transfixed by odd detail - a bootlace tied just a few hours ago, by fingers that will now never move again. What talents lie locked into the muscle memory of those fingers? Could they, as recently as this morning, have picked out a melody on a piano? With the death of each individual, an entire universe vanishes.

Nevinson's painting shocked the authorities of the day. They had sent him to the Western Front as an official war artist commissioned by the war propaganda department. His earlier work had pleased them. They'd deemed it good for British morale. He'd produced a series of drawings for an exhibition called Britain's Efforts and Ideals. His work depicted stages in the construction of an aircraft and included pieces called Making the Engine and Acetylene Welder - all good, morale-boosting stuff.

He'd come to their attention because of a series of paintings he'd produced early in the war, drawn from his time as a volunteer ambulance driver in 1914-15. They are strikingly modernist in composition.

Image copyright Tate Image caption La Mitrailleuse, 1915, Christopher Richard Wynne Nevinson 1889-1946, presented by Contemporary Art Society

In one, called La Mitrailleuse, or the machine gun, four soldiers - one dead, three living - are depicted at a machine gun post. It is a portrait of this first experience of truly modern war - rooted, as it now was, in mass production and the mobilisation of organised industrial process. In the painting the men are drawn with the same hard, angular, rigid lines as the gleaming silver-grey gun they are operating - the men are robotised to become, with the fiercely powerful weapon they are wielding, complementary parts of a co-ordinated destructive enterprise, humanity absorbed into the killing machine.

"All artists should go to the front," the hawkish Nevinson wrote of this early war experience, "to strengthen their art, by a worship of physical and moral courage, and a fearless desire of adventure, risk and daring, and free themselves from the canker of professors, archaeologists, cicerones, antiquaries and beauty worshippers."

You see this still in modern warfare - men made of vulnerable flesh and blood, whose living fingers hold in their muscle memory infinite talents and skills absorbed into a vast, implacable, mechanised force of nature.

Image copyright IWM Image caption Acetylene Welder (L) and Making the Engine (R) by CRW Nevinson, IWM

One day in the spring of 2003, a few days after the American-led invasion of Iraq and the symbolic toppling of the statue of Saddam Hussein, I came back to my room in the Hotel Palestine, a concrete tower block that looks out over the broad green-brown sweep of the Tigris River and the crashing teeming life of the crowded city beyond.

An arms dump had just exploded in a residential suburb. Nearby houses that had withstood weeks of allied bombardment were obliterated. Families were wiped out. But what was striking was how quickly public anger was channelled. Within an hour there was a "spontaneous" demonstration of Iraqis - hundreds, perhaps thousands, strong - already with printed placards and leaflets blaming the Americans for deliberately endangering the lives of Iraqis. I went along. I marched with them, interviewed them for television. One man told me, in fluent English, that "the United States of America is the enemy of Islam, it is written so in the Holy Koran".

I said in my report for that night's news on BBC One:

"The explosion has ignited an anti-American fury. Within hours that fury was organised. It hasn't taken long for this to turn into a demonstration of rage against the Americans. Today, nothing the Americans can say will be heard amid the din - the organised and carefully marshalled chorus - of anti-American sentiment."

Image copyright Tim Hetherington/Magum Photos

And in the middle of this tumult, I came back to the relative calm of my hotel room in the Hotel Palestine. There was no electricity. Sunlight slanted horizontally into the dusty, dim corridors and I saw at the end of the passage, outside my room, two figures silhouetted against the white glare of the sun. As I approached I saw that they were soldiers, their uniforms stained with the mud of the Tigris valley, Americans, for they were cradling US Army assault rifles in their arms.

They were an intimidating presence. Until they spoke. "Sir," one of them said, and there was a quiet, shy deference in his voice. I saw that they were young, achingly young, perhaps 19 years old, lettuce-fresh faces above long, lean, loose-limbed frames - no more than boys in the grown-up garb of desert camouflage. "Sir," he went on, "we heard that there was a satellite phone in this room. We haven't been able to call home in four months."

The boast of heraldry, the pomp of pow’r And all that beauty, all that wealth e’er gave Awaits alike th’inevitable hour. The paths of glory lead but to the grave" Thomas Gray, Elegy Written in a Country Churchyard Getty Images

They were the first in a little trickle of young US servicemen who would come to my room for this purpose in the weeks that lay ahead. What struck me with great poignancy was this - that almost always they phoned their mothers. From the other side of the room you would hear the phone sound in some far place in Kentucky or Idaho. The boy would say "Hi Mom!" and then you would hear the excited, disbelieving scream of delight echoing down the line.

This vast military machine that we had watched assemble itself in Kuwait with its hardware and its discipline and its resolution and unshakeable belief in the virtue of its mission. It was composed, in part at least, of boys who - more than anything - missed their mothers.

I think of those two young men whose names I never learned when I look at Nevinson's Paths of Glory. Its title is taken from Thomas Gray's Elegy Written in a Country Church-Yard. "The boast of heraldry, the pomp of pow'r, / And all that beauty, all that wealth e'er gave / Awaits alike th'inevitable hour. / The paths of glory lead but to the grave."

Government censors did not like Paths of Glory. They judged it bad for morale and refused to pay Nevinson for it. But he included it anyway in the first exhibition of his war paintings in London early in 1918, with a brown paper strip across the canvas carrying the word "censored". He was reprimanded both for exhibiting a censored painting and, bizarrely, for unauthorised use of the word "censored" in a public place. But the painting was bought, during that exhibition, by the Imperial War Museum, where it remains.

What happened to Nevinson, the hawkish young man who had spoken, earlier in the war, of adventure and courage and risk and daring, that he should, by war's end, have abandoned his brutal modernism to produce this gentle, elegiac naturalistic image of two anonymous dead boys in the mud of the Western Front?

I am struck again and again in the war zones of our own age by the tenderness of youth and the brutalising experience of combat and occupation and insurgency. I have become interested in the magnetic pull that war has on the young male imagination.

In the early part of the last century the poet AE Housman addressed this in a little four line poem that is a contemplation of a World War One cemetery. It goes like this: Here dead we lie/ Because we did not choose/ To live and shame the land/ From which we sprung. / Life, to be sure/ Is nothing much to lose, / But young men think it is/ And we were young."

Christopher Nevinson Christopher Nevinson (1889-1946) was an avant-garde British painter

In the years leading up to WW1, he moved to Paris and joined the 'Futurists'

The group was thrilled by speed, technology and modern warfare

After serving as an ambulance driver in the war, he used Futurist techniques to show the horror he'd seen You can watch a slideshow of Christopher Nevinson's works on BBC Your Paintings

Four lines, 39 words, each one in common everyday use, 37 of those 39 words monosyllables and yet the poet manages to make them carry an enormous burden of nuance and sorrow and wisdom and sentiment.

But it is an old man's sentiment. The young are strangers to its undercurrent of regret and loss. In 1915, when the poet Rupert Brooke enlisted, he wrote to a friend that soldiering "is the only life for me now. The training is a bloody bore. But on service one has a great feeling of fellowship, and a fine thrill, like nothing else in the world. And I'd not be able to exist for torment, if I weren't doing it. Not a bad place and time to die, Belgium in 1915? The world'll be tame enough after the war. For those who see it. Come and die. It'll be great fun."

Why do the young - and young men in particular - want to go to war? Why do they dread being left out of their generation's fight? Why, indeed, did I, when the opportunity to become a war reporter arose, seize it?