Prince Hubertus zu Loewenstein, the German historian and diplomat, could never forget June 28, 1914. His parents were sitting in their castle grounds when a footman broke the news that a Serbian nationalist had shot dead the heir to the Austro-Hungarian throne. “Lower the flag,” the senior Loewenstein, who represented a branch of the Bavarian royal family, ordered, pointing to the family standard fluttering on the castle tower, and added in the same breath, “This means world war!” And so it did, despite a flurry of telegrams signed Nicky, Willie and Bertie, the Russian, German and British emperors who were cousins and called each other by their nicknames.