Stocks tumbled on Wall Street Tuesday as a trade war between the U.S. and its key trading partners escalated and threatened to wipe out all the gains for the S&P 500 since Election Day. The Trump administration imposed tariffs on imports from Canada and Mexico starting Tuesday and doubled tariffs against imports from China.

Uncertainty over President Donald Trump’s tariffs rattled Wall Street on Thursday, sending the Dow Jones Industrial Average tumbling by more than 400 points, or 1%.

All three major U.S. markets sank before regaining lost ground on fears a trade war will hobble the world’s largest economy and boost inflation.