Beijing responded swiftly on Tuesday to the tariffs President Trump had promised, announcing a fusillade of countermeasures targeting American companies and imports of critical products. Mr. Trump’s 10 percent tariff on all Chinese products went into effect at 12:01 a.m. Tuesday, the result of an executive order issued over the weekend aimed at pressuring Beijing to crack down on fentanyl shipments into the United States. The Chinese government came back with a series of retaliatory steps, including additional tariffs on coal, natural gas, farm machinery and other products from the United States. It also said it had implemented restrictions on...