By Eric Vandenbroeck and co-workers

The Stunning Failure of Iranian Deterrence

Although it was the United States and Israel that instigated attacks on Iran on February 28, leaders in Tehran deserve some of the blame for failing to effectively deter their adversaries. As the deceased commander of the Islamic Revolutionary Guard Corps Aerospace Force, Amir Ali Hajizadeh, once put it, maintaining deterrence is like riding a bicycle: “You have to keep pedaling all the time, or else the bicycle will fall.” Over the past three years, Iran has started to lose its balance; now it has tipped over.

In recent decades, Tehran developed what it believed was a system of layered deterrence. It invested in conventional forces and air defenses to protect its nuclear program and retaliate against Israel and U.S. bases throughout the region. Through a sprawling network of partners known as the axis of resistance - Hezbollah in Lebanon, Hamas in Gaza, Houthi forces in Yemen, and Shiite militias in Iraq - Iran promised to escalate any attack on its homeland into a regional affair. And Iran’s nuclear program would function as the ultimate backstop. Tehran hoped that the mere development of an advanced civil nuclear program - not an actual weapon - would make the country too dangerous for adversaries to ignore, even as the ambiguity of the program would make it hard for adversaries to justify an attack against it. If necessary, Iran’s civilian nuclear program could be quickly repurposed for military use.

Iran’s strategy worked for a time. But over the past few years, Tehran made a series of errors that proved deadly. It revealed the limits of its missile force and depended too much on its network of proxies for protection. It curbed its nuclear ambitions at what in hindsight appears to have been the most inopportune moment: when Iran was close enough to developing a bomb to invite a preventive attack but not close enough to deter one. It also publicized the progress it was making in technologies relevant to building nuclear weapons instead of holding its cards close to the chest.

Each of these errors compounded the others. Together, they led to the disaster now unfolding. For Iran’s leaders, the lessons are clear: deterrence cannot be outsourced to proxies; threats, if not credible, risk inviting retaliation; and a latent nuclear program is hardly a substitute for actually having the bomb.

 

Going Ballistic

Iran’s ballistic missile arsenal was, for a time, the most credible pillar of its deterrent. Over the past two decades, Tehran has built the largest missile force in the Middle East, consisting of thousands of short- and medium-range ballistic missiles designed to strike Israel, U.S. bases, and Gulf infrastructure. Iran’s Aerospace Force hoped to threaten mass salvos that would be capable, in theory, of saturating Israeli and U.S. missile defenses. But as soon as Iran put its missiles to use, it demonstrated the limits of its arsenal. In April 2024, in response to an Israeli attack on the Iranian embassy in Syria, Iran launched missiles at Israel for the first time. It did so again in October 2024. During both instances, Israel intercepted almost all the missiles, and U.S. and Israeli defense planners learned more about Iranian capabilities and tactics than they ever could have through satellite surveillance or signals intelligence. Iran was, in effect, conducting live-fire training exercises for its enemies’ benefit.

Israel drew on those lessons to wage the 12-Day War in June 2025, which was aimed at destroying Iran’s nuclear program. (The United States joined the campaign, dropping enormous bombs on nuclear facilities buried deep underground.) During the confrontation, Iran launched approximately 500 missiles at Israel; Israeli forces reported that only 31 landed in populated areas. Meanwhile, the Israeli air force took out hundreds of Iranian missiles, eliminated roughly half of Iran’s estimated 400 mobile missile launchers, and killed around three dozen IRGC commanders. Over those 12 days, Iran revealed its weaknesses, used up much of its weapons stocks, and, ultimately, failed to limit escalation - finding itself on the receiving end of immense American firepower.

After the June 2025 cease-fire, Iran frantically tried to replenish its stockpile of missiles. By early 2026, U.S. intelligence assessments suggested that it had rebuilt somewhere between 2,000 and 2,500, with dozens more being produced monthly. (Some of its missile factories survived the U.S.-Israeli onslaught because they were built underground.) But restocking without changing strategy was a bad plan. Iran was doubling down on what had already failed and giving its adversaries an excuse to launch another attack. Israel tracked Iran’s effort to restock and appears to have convinced the United States around the end of 2025 that Iranian attempts to reconstitute its ballistic arsenal and its nuclear infrastructure warranted another set of strikes.

As the effectiveness of Iran’s ballistic missile capabilities diminished, so, too, did the usefulness of its proxies. Iran had used proxies to complement its own deterrence capabilities. The groups caused trouble for the United States and Israel across Iraq, Lebanon, and Syria, and provided the ultimate threat: attack Iran, the entire Middle East would erupt. Tehran invested enormous resources into cultivating, training, arming, and coordinating its proxies, treating them as the outer perimeter of its defenses.

But the groups became a liability as they prioritized their own agendas over Tehran’s directives and dragged Iran into fights it didn’t want. Iran probably did not have advanced knowledge of Hamas’s attack on Israel on October 7, 2023. After the attack, Israel systematically pummeled Iran’s proxies: Hamas in Gaza, Hezbollah in Lebanon, and the Houthis in Yemen. By 2026, the axis that was meant to shield Iran left it exposed. And by arming Hezbollah, backing Hamas, and directing Houthi strikes on Gulf shipping, Iran consolidated a coalition of adversaries - Israel, the United States, and key Arab countries - that would otherwise have remained divided.

 

The Nuclear Option

Perhaps Iran’s most consequential error was its approach to nuclear weapons. For years, Tehran pursued a so-called threshold strategy: it sought the technical know-how and infrastructure to build a nuclear weapon without actually building one, partly out of an interest in compelling the United States diplomatically to provide sanctions relief. During the 2010s, Israel tried to delay Iran’s program through sabotage and assassinations. The United States, under the Obama administration, used diplomacy. In 2015, Iran signed the Joint Comprehensive Plan of Action (JCPOA), in which it traded restrictions on its nuclear program for sanctions relief.

The JCPOA was, paradoxically, the beginning of Iran’s undoing. The agreement shed light on Iran’s nuclear infrastructure. Under the deal’s terms, Iran agreed to let inspectors from the International Atomic Energy Agency monitor its program, resulting in regular reports that detailed centrifuge numbers by hall, exact enrichment levels, and stockpile quantities at every declared nuclear facility. The signatories reasonably believed that clarity would remove doubts about the peaceful nature of Iran’s nuclear program.

But such transparency became a problem for Tehran in 2018, when the first Trump administration unilaterally abrogated the deal and reimposed sanctions. Iran had given away valuable information about itself and was getting little in return. It eventually pulled out of the deal, too, and restarted activity that had been banned, pushing itself gradually closer to the threshold of a nuclear weapon. Tehran publicized its nuclear advances in the hope that its progress could be used as leverage over Washington. In 2019, Iran announced that it had breached the agreement’s enrichment limits and began regularly issuing official statements on its breakthroughs, which included details about facilities, centrifuge types, and approximate stockpile sizes.

Iran made hundreds of pounds of near-weapons-grade uranium and began producing uranium metal, a key industrial step necessary in the manufacture of a bomb. By early 2025, almost seven years after the first Trump administration violated the JCPOA, Iran was in a position where it could theoretically produce enough weapons-grade uranium for a single nuclear weapon in under a week. It possessed enough uranium to, if enriched just a bit more, sustain roughly nine or ten weapons. It was, without a doubt, the non-nuclear state closest to getting the bomb.

But by letting everyone know the gradual nuclear progress it was making, Iran made itself more vulnerable to attack. There are two ways a country on the cusp of having nuclear weapons can protect itself. The first is ambiguity: concealing its nuclear program so that adversaries cannot confidently assess whether a strike would knock out the nuclear program, how quickly it could reconstitute its capabilities, or whether it might already possess a nuclear weapon in secret. In that case, adversaries must plan for the worst. Israel itself has taken this approach by neither confirming nor denying that it has nuclear weapons.

The second way is to make a nuclear weapon so quickly and covertly that by the time adversaries recognize the threat, it would already be too late for a preemptive strike. After the collapse of a U.S.-North Korean nuclear deal in 2002 and the U.S. invasion of Iraq in 2003, Pyongyang rushed a weapons program in secret and tested a device before other countries could organize a decisive response. Once a country has a bomb, its adversaries’ calculus shifts. An attack at that point is no longer preventative; it risks nuclear retaliation.

Both pathways require opacity, which Tehran had relinquished by agreeing to the JCPOA and trumpeting its nuclear progress once the United States had left the deal. The United States and Israel had the confidence to strike Iran’s nuclear program in 2025 and 2026 in part because they knew almost exactly what they were up against. Iran’s error wasn’t getting close to a bomb; it was in revealing too much about its capacities along the way.

 

New Rules

Iran wasted its conventional and proxy forces by treating them not as guardians of its nuclear program but as tools of offensive regional competition. Its network of partners that was supposed to make Iran too costly to strike had, by 2026, made it conspicuously vulnerable. The missile arsenal that was supposed to threaten devastating retaliation had been prematurely spent. All Iran had left was its latent nuclear program, but even that failed because the regime divulged details that should have been kept secret.

The failure of Iran’s deterrent invited a devastating regional war. Tehran wanted the benefits of a nuclear weapon without the actual weapon. It wanted the power of a regional proxy network without the discipline to husband it carefully. These contradictions compounded until the structure Iran had built for four decades gave way all at once.

The current war may end with an Iranian leadership in place that remains resolutely hostile to Israel and the United States. If such a regime decides to pursue nuclear weapons, it will likely have learned to keep its nuclear activity under wraps and to disperse sensitive nuclear equipment and materials. It will have also probably concluded that remaining indefinitely at the nuclear threshold is more dangerous than crossing it. It therefore may create the conditions to rapidly build a nuclear weapon in secret: maintaining smaller stockpiles of highly enriched uranium, preserving centrifuge expertise, and developing the technical components required for weaponization in ways that are harder for inspectors and intelligence services to detect. Iran’s nuclear future may come to resemble that of North Korea’s after 2009, which was the year that inspectors were evicted from that country, never to return since.

For the United States, the lesson is a deeply uncomfortable one. Wars fought to prevent proliferation can end up accelerating it, by making the bomb look more valuable - and not just to the country being targeted. Governments watching the destruction of Iran will draw the same conclusion that North Korea did years ago: a nuclear weapon is essential to prevent an attack from the United States. The very transparency that nonproliferation agreements demand will come to look, in light of Iran’s fate, like an invitation to be targeted if the United States shifts course. Washington has not yet reckoned with the world made by its war on Iran, one in which the bomb looks more attractive than ever and would-be nuclear states understand the urgency of developing a weapon in secret.

 

 

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