Mr. Trump insists that these actions are his way of standing up for farmers and ranchers. Other nations such as Japan, China and India have charged higher tariffs than the U.S. for importing American farm goods.

The Dow Jones Industrial Average plummeted 2,230 points, or 5.5%, while the S&P 500 plunged 6%. The tech-heavy Nasdaq declined 5.8%. The decline put the Nasdaq into bear market te