Populism and polarisation have weakened the traditional foundations of Western agreement. And within Western societies, the growth of identity politics has caused fragmentation, while non-democratic states including Russia use new technologies to fan the flames of social division. In addition, the temptation of isolationism, particularly in the US, has become a worrying trend. A mixture of domestic disunity, right-wing populism and growing isolationism would be bad at the best of times. But these times are tough geopolitically because they throw up ...