Skirth was born on 11 December 1897 in the Chelmsford registration district and he grew up in Bexhill-on-Sea. In 1916 he volunteered for the British Army during the First World War. He became a Battery Commander's Assistant in the Royal Garrison Artillery, responsible for making the calculations necessary to target the large guns of a field battery. When he argued with a superior officer over whether to use a church for target practice he was demoted in rank from Corporal to Bombardier ("two-stripe and one-stripe men respectively"). He was knocked out by a shell during the Battle of Passchendaele, suffering shell-shock and amnesia before being sent to the Italian Front. There he made a resolution that he would do everything within his power to avoid further loss of human life. He felt that the "just war he had signed up for had been a lie," and was disillusioned with the army and the conduct of the war. In a church in the Italian village of San Martino he made a private pact with God that he would never again help to take a human life. He wrote to his future wife, Ella Christian, explaining that he had become a pacifist and a conscientious objector. He then began a campaign of small acts of sabotage, introducing minor errors into his trajectory calculations so as to mistarget the guns, such that they "never once hit an inhabited target, intentionally anyway, first time". His actions were never discovered by his superiors. He received the British War Medal and Victory Medal for his war service but declined the Military Medal. He and Ella Christian married on 29 December 1924 at the Church of St. Barnabus, Bexhill-on-Sea.

After the First World War, Skirth became a life-long pacifist, arguing that Britain should not have declared war on Germany in 1939 and that he would rather surrender and face occupation by a hostile force than take up arms against them. He had volunteered in 1916 as an idealistic patriot, convinced that "King and Country" were causes worth fighting for, but it was not long before he became disillusioned.

Skirth attributed this disillusionment in large part to the horror of his war experiences, but felt that his Christian upbringing and sense of right and wrong, and his naturally sensitive character, also played significant roles. A self-confessed 'dreamer' with a romantic sensibility, Skirth was very fond of literature, and in particular poetry ... he took with him to the front a much-annotated copy of Francis Turner Palgrave's Golden Treasury, along with Lewis Carroll's Alice in Wonderland and Hillaire Belloc's The Path to Rome. Keats, Shelley and Byron were his favorite poets, and he was also fond of Robert Browning's works. He had an intense love of beauty, which he found all around him ... in music, architecture and the natural world. On the Western Front, he wrote, he "had been deprived of the one thing that to me was as precious as life itself, my love of beauty".

In 1971, having retired from a teaching career, Skirth began writing a memoir which described his conduct and experiences during the First World War. He gave it to his daughter Jean in 1975 and died in 1977.

In 1999 his daughter donated the memoir to the Imperial War Museum. Skirth's story has been featured in the books The Cross and the Trenches (2003) and Casualty Figures (2008) and in Ian Hislop's television documentary Not Forgotten: The Men Who Wouldn't Fight (2008).

In 2010 the memoir was published in book form by Macmillan, as The Reluctant Tommy: Ronald Skirth's Extraordinary Memoir of the First World War, edited by Duncan Barrett and with a Foreword by Jon Snow. The book received largely favourable reviews by Richard Holmes in the Evening Standard and Jonathan Gibbs in the Financial Times as well as coverage in the Daily Mail, Socialist Worker and the Sunday Express.