From Deal to Disaster: How the Collapse of the Iran Nuclear Agreement Sparked a Global Crisis

By Tanush Mohaptra

Few foreign policy decisions in recent history have had consequences as dramatic as the United States' withdrawal from the Iran nuclear deal. What started as a political dispute over a flawed but functioning agreement has snowballed through a series of military escalations, a botched assassination campaign, and a blockaded waterway into one of the most significant geopolitical crises of the 21st century. To understand how we got here, you have to go back to the beginning.

The deal in question, known as the JCPOA, was signed in 2015 between Iran and several world powers including the US, UK, France, Germany, Russia, and China. Under the agreement, Iran significantly reduced its nuclear program and accepted strict monitoring safeguards, while in exchange receiving relief from nuclear-related sanctions. For a few years, it worked. International inspectors verified Iran was complying. Then Trump pulled the US out in 2018, calling the deal rotten. Iran responded by ramping up uranium enrichment, and the region slowly slid toward war.

Things first boiled over in June 2025 with what became known as the Twelve-Day War. Israel bombed military and nuclear facilities in Iran in a surprise attack, assassinating prominent military leaders and nuclear scientists. Iran retaliated with over 550 ballistic missiles and over 1,000 suicide drones. The US helped intercept Iranian strikes and bombed three nuclear sites. A ceasefire brokered by Oman held after 12 days. It was brutal but contained, because the strikes had a defined scope that left room for diplomacy.

That window of opportunity slammed shut fast. After the ceasefire, Iran's economy collapsed further under new sanctions, and by December 2025, massive nationwide protests erupted across Iran, becoming the largest since the 1979 revolution. Security forces responded with a brutal crackdown, killing at least 30,000 people according to Iran's own health ministry. Nuclear negotiations also fell apart in early 2026 when Trump, despite reports of significant Iranian concessions, said he was simply "not thrilled" with the talks.

Then came February 28, 2026. US and Israeli forces began conducting joint strikes on Iran, numbering nearly 900 in just the first 12 hours of what the United States dubbed Operation Epic Fury. This was a fundamentally different operation from the year before. Rather than targeting specific nuclear infrastructure and leaving a diplomatic off-ramp, the strikes killed Iran's Supreme Leader Ayatollah Ali Khamenei, the commander of the Iranian Revolutionary Guard Corps, and Iran's defense minister. Targeting the entire leadership of a nation in one operation is not a move that leaves much room for a quick ceasefire, and that reality has defined everything since.

Iran's retaliation went far beyond what anyone anticipated. For the first time in history, Iran attacked all Gulf Cooperation Council countries: Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the UAE. But the most consequential move was what Iran did to the Strait of Hormuz. Within hours of the strikes, Iran's Revolutionary Guard transmitted warnings to vessels in the strait, stating that no ships would be permitted to pass. Ship-tracking data showed a 70% reduction in traffic almost immediately, and on March 2nd, an Iranian official formally declared the strait closed.

This is where the story stops being just about Iran and becomes about everyone on Earth. The Strait of Hormuz is 21-mile-wide chokepoint between Iran and Oman, and its sea lanes facilitate the transit of around 20 million barrels of oil per day, representing roughly 20% of global seaborne oil trade. Closing it has been described as the largest disruption to the energy supply since the 1970s energy crisis. Brent crude oil prices surpassed $100 per barrel on March 8th for the first time in four years, eventually rising to $126 per barrel at their peak. US gas prices surged past $4 per gallon for the first time in years.

The global economic fallout has been significant. Commodity prices surged across the board, including not just oil but also liquefied natural gas, fertilizer, aluminum, and helium, which is essential for manufacturing high-end semiconductors. Countries like Bangladesh closed universities early, while Pakistan and the Philippines declared four-day work weeks due to energy costs. The ripple effects have hit developing nations especially hard.

Iran has also been strategic about who it lets through the strait. Iran is currently allowing limited passage only to what it calls "friendly nations," including China, Russia, India, Iraq, and Pakistan, while warning that ships linked to the US or Israel could face military action. This is a calculated diplomatic move, essentially using the strait as leverage to drive a wedge between the US and its allies. It has been working to some degree. After America's NATO allies refused Trump's call to help unblock the strait, Trump threatened to withdraw the United States from the alliance entirely, a statement that would have been unthinkable from any previous president, and one that has sent transatlantic relations into a serious crisis.

Now the US appears to be looking for an exit. White House Press Secretary Karoline Leavitt told reporters that reopening the Strait of Hormuz was not a "core objective" of the military operation. Trump himself claimed in a national address that the US imports almost no oil through the strait and therefore is not affected, a statement many analysts called misleading since the global oil market does not care where America sources its oil individually. What matters is the world price, and that price affects Americans too. There are some tentative diplomatic signals worth noting. Iran and Oman are reportedly drafting a protocol to monitor transit through the strait, which briefly lifted stock markets when the news broke. As of April 5th, 2026, Iran has also slightly eased restrictions for Iraq, potentially releasing up to 3 million barrels of Iraqi oil per day back into international markets.

What makes this situation so difficult to analyze honestly is how much of it was foreseeable. When the US left the JCPOA in 2018, experts warned Iran would accelerate its nuclear program, and it did. When the Twelve-Day War ended without a lasting diplomatic solution in 2025, analysts warned there was no real path forward, and there was not. The Strait of Hormuz has been Iran's most well-known point of leverage for decades. Every military and energy expert understood that any serious conflict with Iran carried the risk of a Hormuz closure. The US proceeded anyway, without a clear endgame, without broad allied support, and without a plan for what happens to the strait. Now the world is paying record gas prices, a waterway carrying a fifth of the global oil supply is contested by a country currently under heavy bombardment, and NATO is more strained than it has been in its entire history.

The connection from 2018 to today is difficult to ignore. A working, imperfect deal got scrapped. Iran's nuclear capabilities grew. Diplomacy failed repeatedly. A war started, then escalated, and now the US is attempting to withdraw while the economic damage spreads globally. Whether all of this was inevitable or whether smarter diplomacy could have prevented it is a question historians will debate for a long time. What is clear right now, in the spring of 2026, is that the decision to leave the nuclear deal in 2018 set off a chain of events whose costs are being felt at gas stations from Manila to Munich