Stocks dropped 3% on Wall Street, their worst loss of the year, after China countered President Donald Trump's latest tariff threat by letting its currency weaken to the lowest level in more than 10 years.
Investors fear that the escalating trade war between the two giant economic powers could do lasting damage to the world economy.
They responded Monday by dumping stocks and shoveling money into U.S. government bonds, which are considered ultra-safe. That sent bond yields sharply lower.
Technology companies, which would stand to suffer in a protracted trade war, took the biggest losses. Apple gave up 5.2%.
The Dow Jones Industrial Average sank 767 points, or 2.9%, to 25,717.
The S&P 500 fell 87 points, or 3%, to 2,844. The Nasdaq fell 278 points, or 3.5%, to 7,726.