I really did not think it possible to shed new light on the First World War – the most written about conflict in history – but, in this remarkable book, Andrew Davidson does just that. For three years, Colonel Graham Chaplin of the 1st Cameronians served on the front line, making him, so far as we can tell, the longest-serving frontline officer of the war. Most every day he wrote to his wife, Lil, whom he’d married a year before the war’s outbreak, and whom he left pregnant with their first child when he sailed to France as part of the British Expeditionary Force.

There have been many collections of soldiers’ letters home. What sets this one apart is how Davidson puts Chaplin’s letters into context. Each chapter begins with Davidson telling the reader both what is happening in the wider war and in the particular battles being waged by the 1st Cameronians. This is followed by Chaplin’s letters covering the same time period and then the terse entries from the battalion war diary, mostly written by Chaplin as well. It’s the contrast between these three that brings home the long grind of war fighting and war waiting to the reader. Chaplin’s letters, which seldom mention the war directly, begin with the breezy confidence of the professional soldier confident of quick victory. But as victory recedes, and Chaplin is passed over for promotion, the letters become passports to sanity, a dialogue with a normality that the war is slowly erasing.

Many parts of the experience of fighting industrial war can be glimpsed between Chaplin’s lines, but what comes across most clearly is the sheer toil of it: the combination of labour, boredom, fear and constant lack of sleep that slowly saps his strength.

With officers killed even faster than the ranks, Chaplin expected to be promoted out of the line. But his querying of staff orders at the Battle of Loos led to his promotion being held back, so he fought on, marching with his men to and from the frontline trenches, fighting through the battles of Mons, Armentières, Loos and the Somme. Writing on 4 August 1917, Chaplin said, “Today is the third anniversary of the war – it seems like the third century to me.”

To the relief of this reader, in 1917 Chaplin was finally promoted out of the front line. He survived the war, living out the rest of his life with his wife and children, and seldom spoke of the war. How can anyone speak meaningfully of such a conflict? Here, long after his death and through the careful editing and contextualising of Andrew Davidson, Chaplin does so.