On Friday, markets loved that the Strait of Hormuz was opened for business. What a difference a weekend makes.On Friday, markets loved that the Strait of Hormuz was opened for business. What a difference a weekend makes.

Early Friday morning, Iran’s foreign minister posted on X declaring the Strait of Hormuz open. President Trump chimed in shortly thereafter: “IRAN HAS JUST ANNOUNCED THAT THE STRAIT OF IRAN IS FULLY OPEN AND READY FOR FULL PASSAGE. THANK YOU!” Just like that, markets shifted. 

But just as fast as the Strait was opened, it was closed again and the state of the war was as tenuous as it’s been since the ceasefire started. On Saturday morning, Iran’s military reportedly said the strait had “returned to its previous state.” A UK maritime authority said it had gotten word of a tanker coming under Iranian fire near Oman. Ships were turning back. 

• Then Sunday night, things got even more heated: President Trump and US Central Command said the US had opened fire on an Iranian ship that had, after hours of warnings, defied the US blockade of its ports. The US said Marines had seized the ship. The Associated Press, citing Iranian state-run media, said Iran vowed a swift response.
• S&P 500 futures dropped sharply as soon as trading opened Sunday evening as confusion reigned in the waterway. Oil futures rose.
• Many of the stocks whose trajectories shifted on Friday — like airlines, cruise companies, energy stocks, and risk-on plays — stood to potentially have their fortunes reversed during Monday trading. 

The Takeaway 

The war in Iran has shown time and time again just how quickly things can change, but investors were hopeful that opening the strait — the most meaningful economic choke point of the war — would at least lead to lower costs, and potentially an eventual end to the war. Now that future has gotten cloudier.