Captain Patterson, of the First Battalion South Wales Borderers, took part in the First Battles of the Marne and the Aisne. He was killed in battle on Nov. 1, 1914, six weeks after an entry admitting that what he had seen was “beyond description.”

Volunteers have been scanning the diaries, which have been available for public view at the National Archives in Kew since the late 1960s. They can contain details that were not allowed to be sent in letters home.

Culture Secretary Maria Miller told the BBC that “the National Archives’ digitized First World War unit diaries will allow us to hear the voices of those that sacrificed their lives,” and that they are “even more poignant now there are no living veterans.”

The last known British veteran of the war, Harry Patch, died in 2009, at the age of 111.

Other diaries have also emerged. Toby Helm wrote in The Observer about the World War I diaries kept in pencil by his grandfather Cyril Helm, a doctor who served with the Second Battalion of the King’s Own Yorkshire Light Infantry. And the Imperial War Museum is working on a larger project to gather diaries from anyone who lived during the war, to be called Lives of the First World War, which is to begin next month.

In late October 1914, Dr. Helm wrote: “Many fell in our frontline trenches, causing awful casualties. Men were buried alive whilst others were just dug out in time and brought to, unable to stand, with their backs half-broken. My cellar was soon packed, but I could not put any wounded upstairs as any minute I expected the place to be blown up.”