EDWARD Thomas came belatedly to the First World War.

The Anglo-Welsh writer was 36 when the conflict started; twice the age of most of his fellow combatants. Had he so wished, he could have spent its entirety in comparative safety behind a desk. In many respects, however, 1914 was for him a transformative year. Hitherto best known as an essayist, critic, editor and prose writer, he determined to devote his time and energy to poetry. After much agonising on the subject, he also decided to enlist, and the following year, Thomas joined up.

By then several other poets had already been killed, including Rupert Brooke, Julian Grenfell and Charles Hamilton Sorley. It was a war, it seemed, that few wanted to miss. Initially, there was no national conscription - nor was there any necessity for it. Where there was adventure to be had and an empire to protect, men flocked to the call on Lord Kitchener's poster: Your Country Needs You.

Loading article content

In his novel Memoirs Of A Fox-­Hunting Man, Siegfried Sassoon captured perfectly the moment between peace and conflict; between what for him was a normal, privileged life and what he would soon experience in a few short weeks. Like so many of his youthful civilian peers, Sassoon had at that point what he described as a "callow comprehension of terrestrial affairs". A couple of months later, in September 1914, he was a trooper in the Yeomanry, having enlisted two days before war was formally declared.

"For me, so far," he wrote, "the war had been a mounted infantry picnic in perfect weather. The inaugural excitement had died down, and I was agreeably relieved of all sense of personal responsibility."

Thus the war began with what writer and publisher IM Parsons labelled Visions Of Glory - the title of the first section of his best-selling anthology Men Who March Away: Poems Of The First World War. It was then - as now - still possible to delude oneself that what one was about to do was right and proper and noble.

For Parsons, the apotheosis of this was to be found in the sonnets of Rupert Brooke. Handsome, charismatic and talented, Brooke, who was born in 1897, represented a generation which was coming into its own. "Now, God be thanked Who has matched us with His hour," opens his poem Peace, "And caught our youth, and wakened us from sleeping."

But he was not alone in displaying a gung-ho attitude. Siegfried Sassoon, "while safe in the Army", recalled reading in The Times newspaper Thomas Hardy's Song Of The Soldiers:

In our heart of hearts believing

Victory crowns the just

And that braggarts must

Surely bite the dust

Press we to the field ungrieving,

In our heart of hearts believing

Victory crowns the just.

Of course, Hardy himself, who was in his seventies, would not be required to bear arms. But his poem was symptomatic of how the war was sold, and bought into, in its infancy. That, though, was soon to change as reality struck home and the first casualties were announced. Thus Parsons's Visions Of Glory chapter was succeeded by sections titled The Bitter Truth, The Pity Of War, The Wounded and The Dead. But from an insensitive - some might say cynical - point of view, the war gave poets a subject and a purpose. Their job, as the guns boomed and the gas was released and the misery of mud-clogged trenches was made real, was to bear witness, to put into words what they had seen.

It was an event uniquely made for poetry. You cannot write a novel while all hell is breaking loose, while you're blackening your face for a night-time raid, or contemplating what might happen when the "Hun" clip a path through the barbed wire preparatory to killing you.

Famously, Norman MacCaig (a conscientious objector during the Second World War), was asked how long it took him to write a poem. "Long poems, two fags; short poems, one fag," he replied. Even in the trenches there were periods of inactivity and boredom, when one could fill up a diary, write a letter or make the first draft of a poem which, if one was spared, could be polished later.

The imperative was to get down on paper an immediate thought. No-one was under any illusion that life hung by a frayed thread. In one memoir after another, survivors matter-of-factly recalled how they could be chatting to a comrade one minute and looking at his dead body the next. This was a mechanised war, and bullets and bombs travelled far to reach their targets. What is also evident is the comparative lack of rancour towards the enemy. After all, many of the poets knew and admired German culture and had visited Germany shortly before war was declared.

One such was Charles Hamilton Sorley, who was born in Aberdeen in 1895. In her introduction to his collected poems - belatedly published in 1985 - Jean Moorcroft Wilson wrote that Sorley was proud of his Scottish origin and "rather detached from the English" and had "no real sense of patriotism towards England". In fact, he was more inclined to direct his sympathy towards Germany, where he had been studying in the early months of 1914. Once, while out walking with his landlady, he heard some German soldiers singing a song about the Fatherland. "And when I got home," he wrote, "I felt I was German, and proud to be a German: when the tempest of singing was at its loudest, I felt that perhaps I could die for Deutschland - and I have never had an inkling of that feeling about England, and never shall."

Sorley was ambivalent at best about the war and found the way the Germans were demonised by the "silly papers" ludicrous and misleading. Writing to an old school friend, he said: "I regard the war as one between sisters, between Martha and Mary, the efficient and intolerant, against the casual and sympathetic. Each side has a virtue for which it is fighting, and each that virtue's supplementary vice. And I hope that whatever the material result of the conflict, it will purge these two virtues of their vice, and efficiency and tolerance will no longer be incompatible."

Unlike Brooke, Sorley was not part of a London literary clique and, consequently, was bereft of champions and connections which, then as now, can be crucial in making or breaking a writer's career and perpetuating his memory. Despite his reservations, Sorley knew that in a war sides must be taken and joined up at the first opportunity. But he hated jingoism and was especially critical of Brooke's naïve chauvinism ("If I should die, think only this of me; That there's some corner of a foreign field that is forever England …").

Sorley wrote: "He is far too obsessed with his own sacrifice regarding the going to war of himself (and others) as a highly intense, remarkable and sacrificial exploit, whereas it is merely the conduct demanded of him (and others) by the turn of circumstances, where the non-compliance with this demand would have made life intolerable." What Sorley detected in Brooke - whose work he had previously admired - was a seam of sentimentalism.

As Sorley's best poems show, he was under no illusions about the war, knowing only too well what it entailed and what its consequences were likely to be:

When you see millions of the mouthless dead

Across your dreams in pale battalions go,

Say not soft things as other men have said,

That you'll remember. For you need not so.

Sorley was killed in October 1915 at Loos, "probably the last of the First World War poets not to have received full recognition", according to Jean Moorcroft Wilson, and - in the opinion of the late poet laureate John Masefield - "potentially the greatest poet lost in the war". That even in Scotland his name is not as well known as those of Owen, Brooke and Sassoon is all too typical and predictable. It may have been a British war but for many it was the England of a romantic, Constable idyll that was under threat.

Sassoon, for example, was painfully conscious of this while killing hours in a trench. "I was huddled up in a little dog-kennel," he writes in Memoirs Of An Infantry Officer, "reading Tess Of The D'Urbervilles and trying to forget about the shells which were hurrying and hurrooshing overhead. I was meditating about England, visualising a grey day down in Sussex, dark green woodlands with pigeons circling above the tree-tops; dogs barking, cocks crowing, and all the casual tappings and twinklings of the countryside."

Soon, however, Sassoon would be dealt his get-out-of-jail card, being dispatched as "shell-shocked" to Craiglockhart Hospital in Edinburgh. There he encountered like-minded Wilfred Owen, who was suffering from trench fever and concussion. It was one those "strange meetings" peculiar to wartime. Both Sassoon and Owen had come to appreciate not just the pity of war but its futility. Moreover, they had seen at first hand the meaningless slaughter, heard spouted the patriotic cant and been ordered around by witless commanders.

Also at Craiglockhart was Robert Graves, who managed to convince the authorities that Sassoon was suffering from shell-shock when clearly he was not. Thus Graves prevented Sassoon from being court-martialed after he had sent a letter in July 1917 in "wilful defiance of military authority", stating that he believed the war was being deliberately prolonged by those who had the power to end it. It was a courageous and impassioned act, directed at faceless, irresponsible politicians who, for all their admiration of and sympathy for those they were sending into battle, had little real appreciation of what it actually entailed. War, however it is spun, is dirty work, but the lessons that Sassoon and others hoped to impart fell on deaf ears. And so it has gone on for generations, as we can see in Syria, Crimea and Afghanistan.

Eventually, Sassoon was released from Craiglockhart and sent to Palestine, from where he almost felt nostalgia for his life in the trenches. Owen returned to the Western Front in 1918, winning the Military Cross and commanding a company. With a "boy lance-corporal" as his sergeant-major, he wrote on October 4, 1918: "I captured a German machine gun and scores of prisoners … My nerves are in perfect order." Exactly a month later, he was no more.

What survives are his poems, testimony to the nonsense spread by those who insisted that the 1914-18 conflict would be the war to end all wars. Soon there would be another war, one in which there would be even more carnage, greater depravity and senseless slaughter. For perhaps inexplicable reasons, its poets were not of the quality of its predecessor, though there were many poems written about it. But as the 20th century progressed, poetry succumbed to memoir and fiction as the means of depicting man's cruelty to his fellow beings.

Where the First World War gave us Owen's Dulce Et Decorum Est, Sassoon's Suicide In The Trenches and WB Yeats's An Irish Airman Foresees His Death, the Second World War was notable for Anne Frank's diary, Joseph Heller's Catch-22 and Primo Levi's If This Is A Man.

As Hugh Haughton, editor of Second World War Poems, has said, the poetry of the Second World War "has nothing like the same currency as that of the First", when - in the words of Robert Graves - there was a "boom for war poetry". Certainly, one can't help but sense when reading Edward Thomas's war diary the urgency to translate experience to the page. Like so many of the poets mentioned previously, he realised it would be pointless to delay writing. In entry after entry he made notes which could later, if he were spared, be the raw material for poems. On April 5, 1917, he wrote:

The light of the new moon and every star

And no more singing for the bird …

I never understood quite what was meant by God

The morning chill and clear hurts my skin while it delights my mind.

Neuville in early morning with its flat straight crest with trees and houses - the beauty of this silent empty scene of no inhabitants and hid troops, but don't know why I could have cried and didn't.

Early the next morning, Thomas was struck and killed by a shell, one of the 300,000 or so ­casualties of the Battle of Arras.