Siegfried Sassoon's handwritten account of the first day of the Battle of the Somme has gone on display at Cambridge University Library.
It is just one of many personal papers, never before seen by the public, and bought by Cambridge University Library in 2009 for £1.25 million.
The archive includes the first draft of his 1917 statement, protesting at the continuation of the war.
Visitors can see the originals at the library from 21 July 2010.
Sassoon was one of the leading World War I poets but, unlike Wilfred Owen or Rupert Brooke, he survived.
John Wells at the Siegfried Sassoon exhibition at the University Library
He joined up as soon as he could, and was commissioned into the Royal Welch Fusiliers as a Second Lieutenant and sent to France in 1915. He served through the Battle of the Somme, was wounded and was twice decorated for bravery.
The exhibition includes his wartime diaries, which reveal first-hand accounts of the Battle of the Somme and other major World War I battles. In them he details the fighting - and the boredom.
"A lot of people would have written letters home or kept diaries, very few of which have survived nowadays," John Wells, from the department of manuscripts at the University of Cambridge Library, explained.
"So to have Sassoon's diaries and his letters from the front means we're getting not only the view of a famous writer, but we're getting one more individual's account of what when on."
By 1917 Sassoon was appalled by the continuing slaughter and was fearful there was no end in view.
"He had seen generations of his battalion killed around him," John Wells said. "The war is a carnage which is continuing without any end in sight. He is convinced it would be possible to end the war with negotiations, so he writes his soldier's statement.
A fair copy of Siegfried Sassoon's soldier's statement in his own hand
"In it he blames the politicians for continuing the war when it could be ended."
The archive, purchased in 2009, includes his draft of this statement, complete with crossings-out, and is on display at the library.
It was first read out in the House of Commons and then published in the Times.
People were appalled that a decorated officer and published poet was claiming the war was being deliberately prolonged by the government.
Craiglockhart War Hospital
At the time Sassoon was recovering from wounds in England.
Two telegrams were sent to him, recalling him back to the front, which can also be seen in the exhibition.
When he ignored them he expected to be court-martialled, but instead he was sent to Craiglockhart War Hospital, which specialised in helping shell-shocked officers.
"By being sent off to the hospital he's being brushed under the carpet and he's not happy," said John Wells. "He writes letters to his friend Edward Dent - we've got one in the exhibition here - complaining about it. He'd have preferred to have made a bigger splash."
In the end Sassoon returned to the front and was once again wounded in action.
Pictures and poetry
Close-up of an illustrated poetry book a young Sassoon made for his mother
After the war he continued to write poetry and prose, including Memoirs of a Fox-hunting Man, while in Memoirs of an Infantry Officer he became the foremost British chronicler of World War I.
Cambridge University Library already had an extensive collection of Sassoon papers, and the addition of the personal archive means it is now the major world centre for Sassoon experts.
Alongside his diaries, visitors can see beautifully-illustrated poetry books, which he wrote and decorated as presents for his mother when he was around 10.
He continued to illustrate his work as an adult.
"In some cases he decorates books to give out to friends," said John Wells. "But this is a book of draft poems, a sort of working note book. He has done a lot of crossing-out, so it's not as if it's a late fair copy. It is clear he delighted in making this combination of poems and pictures in booklets. He did so as a child and did so right until the end of his life."
Sassoon's poetry continues to appeal today, according to John Wells, because: "It is about an astonishing subject, the horror of war, the suffering of the troops, but he's using a relatively straightforward technique. That, I think, is what brings his poetry its power, not only as he was writing it, but for us here today."
The exhibition is at Cambridge University Library until December 2010. It is open Monday to Friday from 9.00am until 6.00pm, and on Saturdays between 9.00am and 4.00pm.
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