Private Alfred Smith, 21, who served with 1st Battalion The Queen’s (Royal West Surrey) Regiment, wrote the eight letters from the western front in 1915.
His letters started on 30 April 1915, just five months before he died near Loos, France, on 22 September.
In one, the soldier of Woking, Surrey, wrote: “Every man is now ready for the mad rush to death, which is for England and Freedom.”
The letters will be sold at Henry Aldridge and Son in Devizes, Wiltshire, on 24 February.
Auctioneer Andrew Aldridge said: “The archive gives us a brutal snapshot of the life of an infantryman in the trenches in 1915.
“For me, its monetary value is outstripped by its historical worth.
“Private Smith was one of the hundreds of thousands of heroes who time has forgotten, but these letters bring his words to life.”
In his first letter, Pte Smith writes: “Well I’ve seen a bit more fighting also a charge or two, sometimes things are a bit hot for us as we are only 100yds apart even when the Germans are shelling.”
He recounts how a comrade was hit close to him and how lucky he had been not to have been wounded.
Pte Smith’s second letter read: “We had five or six charges made from the Germans but we stopped them back each time they got to our trenches leaving hundreds of dead.
“By the time you receive my letter my regiment will be leading a bayonet charge with the hopes of breaking through the German lines.
“Every man is now ready for the mad rush to death, which is for England and Freedom. Excuse this letter as the bombardment has now started and it gives us a nasty shock.”
In another letter, written over two pages and dated 14 June, he gives a vivid account of an attack on German lines.
“It was like hell getting back. I can say I said my prayers when I got over the front of our trench,” he wrote.
On 12 July, Pte Smith wrote how he and his comrades were unhappy as there were married men at the front and single men still at home.
“If a man is wanted for a hot job a single man should always be first, a married man second for they have wives and children to think of,” he wrote.
His final letter was undated, but described the dangerous life of the trenches, recounting how a shell landed in his trench as he was eating breakfast.
The letters come with their original envelopes.
Pte Smith was the son of George and Emma Smith, who lived in Beaconsfield Road in Kingfield, Woking.
He is buried at the Guards Cemetery, Windy Corner, in Cuincy, France, along with 1,250 others.
In total, 8,000 men were killed from the 25 battalions and 31 units of The Queen’s (Royal West Surrey) Regiment during the First World War.
The regiment gained five Victoria Crosses.