For over two hundred years every single European war that Britain has been involved in has originated in the eastern half of the continent. From the Greek War of Independence in the 1820s, to the Crimean War in the 1850s, and from both World Wars – starting with Austro-Hungary’s shelling of Belgrade in late July 1914 and Nazi Germany’s invasion of Poland in September 1939 – to the Bosnian and Kosovo Wars in the 1990s, it has been an iron rule of modern British history that military crises in Europe always come upon us from these eastern lands ‘of which...