ONE hundred years ago this weekend the poet Siegfried Sassoon was entrenched at the Somme and expecting at any moment to meet his maker. The battle that would eventually claim more than a million French, German and British lives was just a couple of days old and Sassoon – known to the men under his command as "Mad Jack" because of his reckless bravery – experienced for the first time since the war had begun “the debris of an attack”.

It was a sight that was to haunt him for the rest of his long life. Lying by a roadside, he saw 50 British dead, many of them Gordon Highlanders. There were countless Germans too. “These dead,” he remembered, “were unlike our own; perhaps it was the strange uniform, perhaps their look of butchered hostility. Anyhow they were one with the little trench direction boards whose unfamiliar lettering seemed to epitomise that queer feeling I used to have when I stared across no-man’s-land, ignorant of the humanity which was on the other side.”

I have lost count of the number of times I have read that passage and the book in which it appears, Memoirs Of An Infantry Officer. It is the sequel to Memoir Of A Fox-hunting Man in which Sassoon wrote about his childhood growing up in rural England, where he was obsessed with horses and hounds. Taken in tandem, the two books articulate more powerfully than any others the chasm that lies between peace and war, normality and chaos, sanity and insanity. Even when in the rat-ridden trenches and gagging on the stench of death, Sassoon tried to recreate that lost Eden, listening to larks, visualising the Sussex downs and “all the casual tappings and twinklings of countryside”, and immersing himself in Thomas Hardy’s Tess Of The D’Urbervilles.

It’s often said that the First World War was the first modern war, such was the industrial scale of the carnage. But it was also a poets’ and prose-writers’ war, when a gifted generation was obliterated by what Wilfred Owen called “the monstrous anger of the guns”. The irony of war is that in the act of destruction it encourages us to create. Put crudely, it is a gift of a subject, especially if you witnessed it firsthand.

Encouraged by Lord Kitchener’s exhortation, “Your Country Needs You”, writers hastened to join up and, after the initial euphoria, soon began to fall like nine-pins. Rupert Brooke, perhaps potentially the brightest and best of them, died of blood poisoning in 1915 on his way to Gallipoli. Julian Grenfell, who joined up immediately on leaving Oxford, was killed that same year.

Lives barely lived were brutally terminated. The war was impersonal, merciless and senseless. Why some survived and others did not defied comprehension. Survivor guilt led many to madness, others to suicide. As the months marched by the dolorous roll-call grew: Isaac Rosenberg, killed in action; Charles Hamilton Sorley, the greatest of the Scottish First World War poets, killed at the Battle of Loos; Edward Thomas, shot at Arras, pen in hand; Wilfred Owen, killed in action on November 4, 1918, a week before the Armistice. Their luck, if such it may be called, had run out.

With death a constant and immediate presence the imperative to write and record undoubtedly contributed to an urgent flowering. Most of the poems by serving soldiers were relatively short because of the circumstances in which they were written. With snipers everywhere, there was an incentive to get things down quickly. Famously, WB Yeats said that “passive suffering is not a theme for poetry” and contrived to omit Owen from The Oxford Book of Modern Verse, published in 1936, on the grounds that his poetry was “all blood, dirt and sucked sugar-stick”, which must be a contender for the most nonsensical thing the Irishman ever wrote.

Owen, of course, owes much of his posthumous reputation to his stay at Craiglockhart hospital in Edinburgh, which is now part of Napier University. There, in 1917, suffering from what we term post-traumatic stress, he was befriended and mentored by Sassoon. Initially gung-ho about the war, Sassoon had published a letter “on behalf of soldiers” calling for it to be stopped, for which he could have been court-martialled, cashiered and imprisoned.

Instead he was sent to Craiglockhart where Owen was already embedded and where the enlightened Dr WHR Rivers was in charge. Luck – that word again – had delivered Sassoon, his nerves shattered, to the right place at the right time. Soon, however, he felt well enough to take Owen under his wing, introducing him to Henri Barbusse’s great anti-war novel, Under Fire, and encouraging him to see poetry as the means to convey the horror of war. Within a matter of weeks Owen progressed from minor to major poet, beginning with Anthem For Doomed Youth, which, like the memory of those so casually sacrificed, age cannot wither nor custom stale.