Stock Market Today: Dow ends 400 points lower, S&P 500 and Nasdaq fall; 10-year Treasury yield hits a 20-month high and oil jumps on new U.S. strikes against Iran

U.S. stock markets declined with the Dow Jones Industrial Average dropping 400 points, while the S&P 500 and Nasdaq also fell. The 10-year Treasury yield reached its highest level in 20 months, and oil prices rose following new U.S. military strikes against Iran.

Why it matters: Geopolitical tensions and rising bond yields contributed to the broad market sell-off.