New tariffs on China went into effect Tuesday as part of President Trump’s effort to use trade measures to halt the flow of fentanyl into America – and Beijing retaliated by announcing its own tax on some imports from the US. The 10% additional tariff on imported Chinese goods came into force at 12:01 a.m., hours after the leaders of Mexico and Canada were able to negotiate a 30-day pause on the implementation of massive, 25% duties on goods bound for the US. Trump, 78, declared last week that the fentanyl crisis in America constituted a “national emergency” and that...