In what many viewed as a symbol for the horrors of the war, with 60,000 British casualties on the first day alone, the Lancashire soldier saved his colleagues from an exploding cart.
He survived the war, winning medals for his quick thinking and bravery, but was reluctant to share the stories of his horrific experiences.
Now, as the centenary is with us, granddaughter Catherine Sargent from Penwortham said she wished she could have she could have found out more from her “hero”.
Mrs Sargent, 52, said she had only learnt about Corporal Marshall through her father, despite living with her grandfather as a child.
She said: “He lived with us from when I was eight to 11, then he passed away.
“But before that he never really used to talk about it - it was my father who told me this story.
“He was born in 1896 so I think he was 18 in 1914 and he was called up.”
Mrs Sargent has this year discovered her grandfather served as a gunner in the Royal Field Artillery, but knows few details of his life through the war.
She said: “All I know is he fought at the Somme.
“His job was to look after the ammunition, so it was a very responsible job and, on one occasion, a bomb must have gone into the cart from the opposition.
“It was a cart they kept all the ammunition in.
“It took a split second decision to push the cart away from all his comrades and himself.
“It blew up, and he saved himself and his comrades.
“If it had blown up there he would have been killed instantly and I wouldn’t be having this conversation so I feel very lucky.”
Corporal Marshall won three medals for his role in the war, although one has been lost.
Mrs Sargent said: “He definitely got a bravery award for pushing the cart away.
“I would definitely say he was a hero - the fact he got promoted to corporal as well, and getting the bravery award.”
She said she wished she could have spoken to her grandfather more about what had happened.
She said: “I think it affected him so much, he was very quiet.
“I wish I’d had chance to ask him about it, but I was only eight and I didn’t think to ask questions like that.
“It never crossed my mind really.”
Corporal Marshall was buried at St Mary’s Church in Penwortham after his death in 1972.