Oil Jumps, SK Hynix Slumps as US Strikes Hit Iran Again

Oil prices jumped and world shares turned mixed on Monday after the United States carried out fresh airstrikes on Iran and Tehran fired back at targets across the Middle East. Brent crude, the international benchmark, climbed as much as nearly 5% in early European trading before settling back to trade up 2.3% at $77.72 a barrel. U.S. benchmark crude added 2.1% to $72.92 a barrel as traders weighed how far the fighting might spread.

The jolt landed on a market already nursing a separate wound. SK Hynix, the South Korean memory chipmaker that pulled off the largest-ever U.S. stock debut by a foreign company just three days earlier, watched its Seoul-listed shares slump 15.4% on Monday. Rival Samsung Electronics fell 10.7%. Tokyo’s Nikkei 225 lost 1.9% and Seoul’s Kospi dropped 9% to its lowest level since early May.

A Container Ship in Flames Reignites the War

The renewed fighting began after Iran struck a Cyprus-flagged container ship transiting the Strait of Hormuz, setting it ablaze and leaving a crew member missing. U.S. Central Command said Iran’s Islamic Revolutionary Guard Corps “blatantly attacked” the vessel as it moved along a route hugging Oman’s shoreline, one commonly used by ships trying to avoid Iranian territorial waters. Oman’s maritime authority said it rescued 23 crew members, all of them Indian nationals, but one remained missing, and India’s foreign ministry said it was working with Oman to find him. The United Kingdom Maritime Trade Operations center said the crew abandoned the vessel for a lifeboat after an onboard fire and significant engine room damage. Iran’s Revolutionary Guard said the ship had ignored warnings to follow an approved route and was struck by a warning shot and brought to a stop.

The attack set off a chain reaction that has now repeated for three straight weekends. The U.S. launched its third round of airstrikes in a week, hitting close to 140 targets including missile and drone launch sites, ammunition depots and communications equipment, according to Central Command. Iranian state media reported explosions along the country’s southern coast near Bandar Abbas and Qeshm island, and a semiofficial news agency said a navy officer was killed.

Iran answered with a wave of retaliatory strikes across the region, hitting sites in multiple Gulf Arab states. The Revolutionary Guard also claimed a strike on an air base in Jordan, saying it destroyed a command-and-control center and drone hangars there. Missile alerts sounded across several Gulf Arab nations early Sunday. Iran said the strait was closed until “calm is restored,” while the U.S. military and President Donald Trump insisted it remained open.

Washington Hits Back, Tehran Vows to Answer

The fighting has pushed the two countries close to abandoning the interim arrangement reached after February’s war, when the U.S. launched an air and maritime campaign against Iran known as Operation Epic Fury, according to a congressional analysis of the conflict’s impact on Hormuz. That war set a 60-day window to negotiate a permanent end to hostilities that began Feb. 28. The latest clashes have left those negotiations in danger of collapse. Defense Secretary Pete Hegseth framed the new strikes as punishment, writing in his own social media reaction to the strikes on Iran that Iran made a poor choice and would now pay.

The era of one-sided deals is OVER. We told you: keep your word or pay the price. Reality is knocking.

Mohammad Bagher Qalibaf, the speaker of Iran’s parliament and one of its main negotiators, posted that message Sunday as Iran carried out its retaliatory strikes. His words followed a defiant address from Iran’s new Supreme Leader, Mojtaba Khamenei, delivered after his father, Ayatollah Ali Khamenei, was buried. The elder Khamenei was killed in U.S.-Israeli airstrikes in February. The new Ayatollah vowed to avenge “the blood of the martyred leader,” and Iran’s retaliation reached across the Gulf within hours, hitting:

• Bahrain
• Kuwait
• Qatar
• Jordan
• Oman

Oil Spikes, Then Gives Back Most of the Move

Both crude benchmarks had drifted back toward pre-war levels after an interim agreement let ships resume transiting the strait. Monday’s strikes erased that calm within hours.

The Strait of Hormuz explains why traders react so fast to any trouble there: it is one of the busiest oil chokepoints on Earth, and few alternative routes exist if it is ever closed for real. The U.S. military said more than 140 ships had transited the strait over the past week. A multinational body overseen by the U.S. Navy said nearly 140 vessels moved through daily before the war, with traffic now continuing “at reduced levels” on both the Omani and Iranian sides. About a fifth of all traded oil and natural gas passed through the strait before the war began, and Iran’s grip on it triggered a global energy crisis, though prices have fallen sharply since wartime highs of $120 a barrel.

World shares were mixed as the strikes rippled through Monday’s session. European benchmarks in Frankfurt, Paris and London nudged higher, Asian markets swung more sharply after the weekend’s fighting, and Wall Street futures split the difference ahead of the New York open.

Wall Street’s Newest Blockbuster Debut Meets a War

Three days before the latest strikes, SK Hynix had pulled off the largest-ever U.S. stock debut by a foreign company, selling 177.9 million American depositary shares at $149 each to raise roughly $26.5 billion. The stock jumped 13% on its Nasdaq debut Friday. SK Hynix Chairman Chey Tae-won called it “a kind of dream” come true in an interview with CNBC. The Seoul-listed shares had already surged more than 600% over the past year on euphoria around artificial intelligence. By Monday, that momentum had reversed hard, at least in Seoul.

SK Hynix’s Seoul-listed stock slumped 15.4% Monday, and Samsung Electronics, its larger domestic rival, sank 10.7%. The declines mirrored the broader Kospi, which dropped 9% to its lowest level since early May. The reversal landed on the same trading day that Brent crude jumped following Iran’s retaliatory strikes across the Gulf.

• Demand: the U.S. share sale drew demand more than seven times the shares on offer, Reuters reported.
• Valuation gap: Micron Technology trades at a forward price-to-earnings ratio of 6.66 times, versus 5.5 times for SK Hynix.
• HBM forecast: the high-bandwidth memory market is expected to grow from about $65 billion this year to $120 billion next year and about $290 billion by 2030, according to Futurum Equities.
• Equipment spend: 11.9 trillion won is earmarked for extreme ultraviolet lithography gear due for installation by the end of next year.

The listing’s own paperwork ties the timing together. SK Hynix said proceeds would fund a new fabrication plant and an advanced chip packaging facility in South Korea, alongside the new lithography equipment. The Nasdaq debut was also meant to narrow SK Hynix’s valuation gap with U.S. rival Micron, whose direct access to American investors has long given it a premium despite holding less market share in key memory products. The company’s American shares carry the ticker SKHY as of Monday, replacing the temporary “when issued” symbol used since Friday’s debut.

SK Hynix’s offering ranks behind only SpaceX’s $75 billion initial public offering last month, the second-largest stock sale in the world, according to The Wall Street Journal. Its American shares carried a market capitalization of $1.193 trillion in real-time exchange data at Friday’s close, before Monday’s Seoul-listed slide.

The AI Trade’s First Real Stress Test

Concerns about the durability of the AI-fueled memory rally predate Monday’s fighting. SK Hynix has said it plans to double its production capacity, or possibly more, to keep pace with demand for the high-bandwidth memory chips that power AI processors. Ipek Ozkardeskaya, an analyst at Swissquote, has warned that technological breakthroughs, more efficient AI models or simply a slowdown in AI infrastructure investment could quickly flip the market into oversupply. The “Magnificent Seven” tech giants, including Nvidia, Microsoft and Amazon, traded at their lowest levels in a decade relative to the S&P 500 this week, according to Morgan Stanley.

The reason why this stock, along with other memory chipmakers, has gone parabolic is that AI demand has somehow created the perception that a sector historically defined by boom-and-bust cycles could remain permanently in the boom phase.

Ozkardeskaya made the comment in a client note as chip stocks wobbled, and SK Hynix’s own numbers are large: net income hit 40.34 trillion won, or $26.6 billion, in the first quarter of 2026. The company joined Samsung Electronics and Micron in May in the small club of chipmakers valued at more than $1 trillion, after SK Hynix and Samsung both signed on to a $1 trillion AI investment initiative announced by South Korean President Lee Jae Myung, pledging $518 billion with suppliers to build two new chipmaking facilities. None of that stopped Monday’s slide in Seoul.

Why Bond Yields Tie It All Together

Behind both stories sits the same worry: interest rates. Higher bond yields have been weighing on financial markets worldwide, since more expensive oil and elevated inflation could push the Federal Reserve and other central banks toward raising interest rates.

Higher rates can help tame inflation, but they also slow economic growth and pressure the prices of all kinds of investments, from tech stocks to newly listed chipmakers. In currency markets, the dollar rose to 162.01 Japanese yen from 161.72 yen, and the euro rose to $1.1435 from $1.1408. The moves followed a stronger Friday session, when the S&P 500 rose 0.4%, the Dow Jones Industrial Average added 0.3% and the Nasdaq composite climbed 0.3% on investor appetite for winners of the artificial intelligence boom.

This week brings earnings from some of the biggest U.S. banks, including Bank of America, Citigroup, JPMorgan Chase, Goldman Sachs and Wells Fargo, all reporting Tuesday. Investors will be watching whether corporate profits are growing fast enough to justify stock prices that remain broadly near records. Tuesday’s results will be the market’s next data point after a Monday that opened with airstrikes and closed with earnings season just getting underway.