EVEN BEFORE President Donald Trump declared a trade war on the whole world, this was a noisy time in global power politics. The din of armed conflict is unrelenting in Europe, the Middle East and Africa. In Asia, Chinese sabre-rattling grows ever louder. Every other week, or so it seems to China’s anxious neighbours, the People’s Liberation Army sends fighter jets and warships to encircle the island of Taiwan, or to stage shows of force in contested seas to China’s east and south. Relishing his role as commander-in-chief of the most potent armed forces in history, Mr Trump makes threats to destroy utterly opponents that defy his demands, from Houthi insurgents disrupting shipping in the Red Sea to drug-smuggling cartels in Mexico.