For many historians there is an understandable temptation to focus on the events which directly relate to their own countries. In the early days of the Great War in 1914 the British made a relatively small contribution to the Western Front and it was the French who were involved in the vast majority of the fighting. Simon House in Lost Opportunity sets out to explain a key event in the failure of the French to stem the German invasion in 1914. This excellent book deals with the Battle of the Ardennes in August 1914; a battle relatively unknown in the UK. Dr House’s great triumph in this book is his ability to explain in clear terms the details of the action and to relate this to the preparations of the German and French before the war. He effectively demonstrates the failure of the French to effectively prepare for the war and the factors involved in this. It was not that the Germans were military geniuses it was just that their preparations for and approach to war were far better than those of the French in 1914. It is joy to find a book accompanied by a separate set of excellent maps which make it considerably easier to follow the detailed account of 22 August 1914. This is a book which greatly enhances an understanding of the events of the early stages of the Great War. I look forward to Dr House’s future books on the French Army which will hopefully include further analysis of the pre-war French Army.