The details of the tariffs are still unclear, which is one reason the markets are so on edge. Political leaders are on edge as well, because Mr. Trump has made clear that the tariffs will fall on adversaries like China as well as nations that, until recently, were considered America’s closest defense and intelligence allies.

Trump has repeatedly called April 2 “Liberation Day,” with promises to roll out a set of tariffs, or taxes on imports from other countries, that he says will free the U.S. from a reliance on foreign goods.

Two months into his White House return, Trump has imposed tariffs on goods from neighboring Canada and Mexico as well as China, all steel and aluminum imports, and foreign cars and auto parts. He's threatened several other countries including traditional allies in the European Union with other steep tariffs ‒ even on European wine.