The Brown Brethren tells the story of friends and comrades who fought together during World War I on the Western Front. The principal characters belong to the London Irish Rifles, a volunteer regiment whose 1st Battalion was mobilized immediately with the outbreak of the war. The 1st Battalion, to which this story's characters belong, especially distinguished itself at the Battle of Loos in 1915. This book takes the men up through the Battle of the Somme (1916.)