The long-simmering clash between the world's two great powers is coming to a head, with dangerous implications for the international system. China has succumbed to hubris. It has mistaken the soft diplomacy of Barack Obama for weakness, mistaken the US credit crisis for decline, and mistaken its own mercantilist bubble for ascendancy. There are echoes of Anglo-German spats before the First World War, when Wilhelmine Berlin so badly misjudged the strategic balance of power and over-played its hand. Within a month the US Treasury must rule whether China is a "currency manipulator", triggering sanctions under US law. This has been...