Nowhere was the legacy of the Great War more profound than in the unleashing of nationalist fervour across Europe. David Reynolds argues that the war made national identity a stark either-or issue, a matter of 'us' versus 'them', and he traces the recurrent struggle between nationalist uprisings and empire-building by Hitler, Stalin and latterly the European Union in the century since 1914.

The Great War shattered the old empires that had ruled central and eastern Europe for centuries and, in 1918, nationalist politicians seized their moment. David travels to the Sudetenland in the Czech Republic and to the Palace of Versailles to explore the drastically changed map of middle Europe in 1919. He explores how the new nation states hastily patched together from the ruins of the Habsburg Empire destabilised the whole European continent for much of the 20th century.

Reynolds finds that Britain's experience of the frenzy of nationalism was very different. The British Empire grew after the Great War and bonds with dominions like Australia and Canada, whose men fought heroically in the war, were renewed. England's union with Scotland and Wales, severely strained just before the Great War, was actually strengthened by the conflict and has only very recently been challenged by resurgent Scottish nationalism.

The grim exception in the British story was Ireland. Comparing the troubled relationship between Czechs and Sudeten Germans in interwar Czechoslovakia to Britain's intractable problems in Ireland, David travels to Dublin and Belfast to examine how two blood sacrifices of 1916 - the nationalist Easter Rising and the 36th Ulster Division's terrible losses on the first day of the Battle of the Somme - aggravated tensions that remain to this day. Show less