My latest book is about the end of the war, the period post-Armistice when the pieces - literally, in terms of battlefield debris and unburied bodies, and psychologically in terms of the lives of the men who had served - were being picked up and a broken, shattered world was slowly being reassembled.
But no book on any aspect of the First War can hope to be complete without at least being informed about its causes, and by the debate that still seems to surround them a century later. For those involved, for the families affected, for the industries and economies ruined and not least for the men (and woman, and children - as early as December 1914 British children were being added to the casualty list) who lost their lives, knowing they were fighting, suffering, dying for a purpose, for a just cause, made the hardships understandable on some intellectual level even if emotionally they were scarcely bearable.
It's not unlike the argument that still surrounds the UK's involvement in Afghanistan and the legacy our troops will leave once their mission is complete. We owe it to the 500 servicemen and women killed as well as the thousands injured to make sure their sacrifice was not in vain.
In hindsight, of course, we know that the 'war to end all wars' was nothing of the sort and that many of the millions who died between 1914 and 1918 did die in vain. We know that thousands of men went to an almost inevitable but wholly unnecessary death as the result of the failures and folly of those in command right up through the forces to the War Ministry and the British Government and the aristocracy.
But should Britain have even gone to war in 1914? What would have happened if we hadn't fought? And what would the map of Europe have been like if, at 11.00p.m. on August 4th 1914 Britain had not declared itself to be in a state of war with Germany?
That's the fascinating question posed by historian Niall Ferguson who refers to World War One as 'the biggest error in modern history' in a recent article in The Guardian. Not that he argues that Britain should never have gone to war. Just that, with a relatively tiny army and without much by way of the resources necessary for a major land-based conflict, we shouldn't have rushed into the conflict as early as we did.
Ah, but the treaties - guarantees of Belgian neutrality and verbal assurances that we would support the French. Well, as Ferguson says, it wouldn't have been the first time (nor the last) that pragmatism, realism or merely blatant self-interest had overridden international obligations.
It's a fascinating thought - the notion that we might still have gone to war with Germany - just later when we were better prepared, perhaps, and with a clearer idea both of what we were doing and why we were doing it. Yes, there were at the time vague designs on parts of the British Empire and some sabre-rattling on the Oceans, but Germany in 1914 didn't pose a serious threat to Britain's homeland security and - arguably - might never have done so.
Of course, such retrospective raking over historical coals is a luxury we can afford. Those fighting, those who had fought and those for whom the Armistice wasn't the end of the war but rather the beginning of a lifetime's struggle to return the land and themselves to normal (or as near as possible) hadn't the opportunity to seriously question what they were doing or why they were doing it. They had to believe they had fought the good fight.
It is their story I am trying to tell. And of course it's a story that knows no future beyond battlefield clearances, beyond a halting resumption of family life, beyond the slow and careful creation of the monumental cemeteries designed to stand for eternity as a symbol of a war that was still thought to have been an end to all wars.
Lest we forget!