A love poem written from the frontline of the Somme by the “great forgotten voice of the first world war”, the American author, heiress, suffragette and nurse Mary Borden, will form the heart of an event at the Tower of London to mark the centenary of Armistice Day.

Borden’s poem, the third in a sequence entitled Sonnets to a Soldier, was written for a young British officer with whom she had an affair while running a field hospital during the first world war. It will be the basis for a choral work by the artist and composer Mira Calix, accompanying a light show that will fill the Tower of London moat from 4-11 November with thousands of individual flames, in the build-up to the 100th anniversary of peace.

Opening: “If you this very night should ride to death / Straight from the piteous passion of my arms,” the poem was not published during Borden’s lifetime. It is, according to Borden expert Professor Paul O’Prey, “the only love poem I know about the battle of the Somme”.

Borden was married to a Scottish missionary with three children when, in 1915, at the age of 29, she persuaded the French army to let her fund and run a field hospital as close to the battlefront as possible. The hospital treated 25,000 soldiers in its first six weeks. In 1916, she met the young British officer Louis Spears, writing of the encounter: “My apron is stained with mud and blood; I am too tired to take it off. My feet are burning lumps as I hobble to open the door. A young officer stands there. He too is splattered with mud; his face is haggard.”

They began an affair; Spears left the love poems Borden wrote to him at the flat of an ex-girlfriend, who sent them to Borden’s husband. “He had had enough – he divorced her and she lost her children for a number of years,” said O’Prey.

In 1929, Borden published The Forbidden Zone, which contained stories and poems about her wartime experiences. “It was my business to know which of the wounded could wait and which could not. I had to decide for myself. There was no one to tell me,” she wrote. The book did not include the love poems, which were only published for the first time three years ago, as Poems of Love and War, edited by O’Prey.

“She wrote a series of extraordinary poems about being at war, including The Song of the Mud. She was very much like Walt Whitman, free-spirited, writing almost a stream of consciousness, an outpouring of thoughts and feelings,” said O’Prey, who was not surprised the love poems weren’t published in her lifetime: “They were quite intimate, personal and passionate – slightly erotic in a very disguised way … too private.”

Borden went on to marry Spears, who became a Conservative MP and a general in the second world war. She set up and ran a mobile ambulance unit that operated across France, north Africa and the Middle East during that conflict.

By her death in 1968, Borden “was already beginning to fall out of fashion as a writer,” said O’Prey. Her work has only recently begun appearing in major anthologies of war poetry, while Poems of Love and War was only her the first solo collection of her work.

O’Prey, who is interested in marginalised voices from the war – those who were there but not fighting - described her as “the great forgotten voice of the war – the outstanding female voice of the first world war”.

“Her poetry can stand alongside anything. These are very powerful statements of witness, and her enormous humanity comes through,” he said. “I’m hoping very much that [the Tower of London installation] will be a significant step in getting her the recognition she deserves.”

Calix, who composed the choral setting for Borden’s work, said: “Often women have been written out of history, and she is one of those who have fallen through the cracks. I wanted the experience [of the choral work] to feel like something we can understand today, and her writing in general does that – it feels really contemporary. When I read war poets, the language feels old now, and there is a distance I don’t feel in her writing … it would be really lovely if people do go back and look at her other work.”