No.2  London, 4 August 1914: Britain declares war on Germany - news that Britain was joining the conflict in Europe was greeted with a delight that would seem inexplicable once the fighting had started. Andy McSmith continues our 100-day series marking the centenary of the First World War

How do you remember a war that destroyed four empires, killed 18 million people and left tens of millions of other lives irreparably broken? Today, as the world prepares to mark the centenary of a conflict that left no corner of the planet untouched, we begin a unique daily series that attempts to make sense of an incomprehensibly huge chapter in human history by distilling it to a mere 100 'moments': episodes, big or small, that in one way or another capture a sense of what it was like to be caught up in the catastrophe of the First World War. Boyd Tonkin introduces our first moment