US stocks have whipsawed through the first half of 2026, with dramatic swings that highlight how geopolitical tensions and sector momentum can reshape markets in months. The Nasdaq and S&P 500 have experienced sharp moves that reflect broader investor sentiment shifts.

March brought a steep selloff as President Donald Trump's escalation with Iran spooked investors, triggering risk-off positioning across asset classes. Defense contractors initially rallied while tech and consumer discretionary names sold off sharply, wiping out early-year gains.

Spring brought an unexpected recovery led by semiconductor shares, which have staged a remarkable rally that pushed major indices back toward record territory. Chip stocks have outperformed broadly, suggesting renewed appetite for growth sectors despite earlier volatility.

Investors now face a market that has proven resilient but remains vulnerable to sudden shifts in policy and geopolitics. The pattern shows that while sectors like semiconductors can drive recoveries, external shocks still carry significant weight in shaping equity trajectories.