At the outbreak of the First World War in 1914 Captain J. L. Jack was serving with the First Cameronians, one of the earliest British regiments to arrive in France. Almost every day while serving in France and Flanders, Jack kept a secret diary. This diary is unique. It presents the detail of a regular officer’s life at war during virtually the whole of the First World War on the Western Front. Jack was witness not only to the horror and wretchedness of much that happened in the trenches but also to the bravery and spirit that kept the British soldiers in the line going through to the momentous battles of 1918 and final victory. Poignant and moving, as well as describing the reality of war on the Western Front, these diaries have been edited and linked with commentaries by the distinguished military historian John Terraine.