Private Walter Hutchinson wrote the poigniant diary in water logged trenches on the first day of the 1916 Battle of the Somme after more than 62, 000 men fell dead or wounded - more than on any other day in British military history.
Pte Hutchinson, of Conisbrough, was a young shop manager when he enlisted for the war as a stretcher bearer in the 10th Battalion, York and Lancaster Regiment.
His diary entries of the Somme battle tell how row after row of soldiers "went over the top" only to be mowed down by German gunfire.
In the first account, written on July 1, he wrote: "German shells was dropping all around... We hadn't gone far up the trench before we casme across three of our own lads lying dead. Their heads had been badly damaged by a shell.
"We had to go scrambling over the poor fellows - in and out, in and out. It was one of the most awful sights I'd ever witnessed.
"Then the order came down dump everything and fix bayonets, you have got to fight for it lads. We obeyed the order like men. But had not gone far when I was hit with a piece of shell."
On July 3 "things seemed to quieten down a bit at teatime so we got to work and dug some graves for our poor comrades."
The diary along with Pte Hutchinson's Military Medal, gold half-hunter pocket watch and several photographs were sold in London last Wednesday through specialist coin and medal auctioneers Dix Noonan Webb.
The items were sold by a relative and were bought by a private collector.
Pte Hutchinson survived the war and returned home where he and his wife Evelyn had a daughter, Constance, in 1919. The couple went on to run a grocer's shop in Maltby before retiring to Cleethorpes where Mr Hutchinson died in his 80s.