The Nasdaq Composite bore the brunt of the selling Thursday, dropping 1.88% to 26,692.87 as investors pulled back from risk assets amid the escalating standoff. The S&P 500 fell 1.11% to 7,718.94, retreating further from its 52-week high of 7,844.52 set earlier this year. The Dow Jones Industrial Average held up better, slipping just 0.09% to 51,621.48, suggesting money rotated into more defensive, blue-chip names while growth and tech stocks absorbed the heaviest losses.
The trigger was news that U.S. military planners have reportedly drawn up strike options against Iran that include the potential use of the so-called "mother of all bombs," one of the most powerful non-nuclear weapons in the American arsenal. Iranian officials have signaled they intend to continue resisting any military action, raising the specter of a prolonged and potentially destabilizing confrontation in a region critical to global energy supplies.
Markets tend to react swiftly to any signal of military escalation involving Iran, given the country's proximity to the Strait of Hormuz, through which a significant share of the world's seaborne oil trade passes. Even the suggestion of U.S. strikes using high-impact ordnance raises fears of disruption to oil shipping lanes, which could send energy prices higher and complicate the inflation picture just as investors already have one eye on elevated Treasury yields and deficit concerns.
Thursday's selloff pushed the Nasdaq further from its own 52-week high of 27,722.75, a reminder of how quickly sentiment can shift when geopolitical risk reenters the conversation after a stretch of record-chasing gains. The S&P 500 and Nasdaq remain well above their 52-week lows near 6,317 and 20,690, respectively, meaning Thursday's drop is a pullback rather than a trend reversal — but traders will be watching closely for any follow-through.
What happens next largely hinges on Washington's actual response and Tehran's reaction to it. Any confirmation of expanded military action, or conversely, signs of de-escalation or renewed diplomacy, could swing markets sharply in either direction in the sessions ahead. Energy markets, defense stocks, and safe-haven assets like gold and Treasurys are likely to be the first places investors look for signals on how seriously to price in the risk of broader conflict.