Donald Trump’s trade officials are run off their feet. China was just the beginning. Since the start of February, the president has announced levies on global imports of aluminium and steel. Reciprocal tariffs, which will charge countries according to their own duties on American goods, and “non-tariff barriers” are set to follow. Allies have been menaced as much as adversaries. America’s closest neighbours, Canada and Mexico, have been bludgeoned by the threat of 25% levies, for the moment postponed after both agreed to boost security at the border.