Joint Israeli and US air and missile strikes on Tehran have killed Ali Khamenei, Iran’s Supreme Leader of 37 years. These strikes were part of a larger US-Israeli aerial attack on Iran across centres of military and political power, which have also killed the Supreme National Security Council Secretary, Ali Shamkhani; Defence Minister Amir Nasirzadeh; and Commander of the Islamic Revolutionary Guards Corps (IRGC), Mohammed Pakpour; among others.The US-Israeli attacks continue. Despite the decapitation of its senior guard, Iran has kept up a sustained region-wide retaliation, targeting US bases in every country of the Gulf as well as Iraq and Israel with drone and missile attacks. Why couldn’t this expanding conflict be prevented?Commitment trapLike in June 2025, the US attacks occurred at the height of indirect but active negotiations between Tehran and Washington, not in their absence. But the key difference is that the current war has arguably broken out due to a breakthrough in talks, not a breakdown. This was evident in that Oman, which traditionally holds discretion to be its most important suit as a serious mediator, broke all precedent early on February 28. Speaking to CBS News, Oman’s Foreign Minister Badr al-Busaidi made the details of US-Iran negotiations public. The details included Iran agreeing to zero stockpiling of nuclear material, down-blending its existing 60% enriched stockpile to irreversible fuel, and allowing US inspectors access to Iranian nuclear sites, among other measures which could be implemented immediately. He asserted that the Obama-era Iran nuclear deal (which US President Donald Trump has always sought to outdo) did not contain such extensive Iranian commitments, making it a significantly better deal from Washington’s perspective. It is reasonably certain that Muscat was aware of Washington’s plan to attack Iran despite the seeming diplomatic breakthrough, reflecting that the White House was operating as if in a commitment trap. For Trump, even a deal with such unprecedented terms would not allow him to save face. The means ultimately spurred their own ends: an attack without any guarantee that the strategic objective of “regime change” could be met, even with decapitation strikes.More in Explained | Bid to undo 1979 Islamic Revolution | Tectonic shifts in Tehran: why they cast long shadow in region, worldIn June 2025, Washington’s casus belli (cause of war) was the destruction of Iran’s nuclear programme. Despite international evidence of Iran continuing to retain 60% enriched uranium, the White House could still use the significant damage at Fordow to maintain that the Iranian nuclear programme was “obliterated” and that “suggestions otherwise” were “fake news”. In February 2026, even as some officials still alleged that Iran was “one week away from a nuclear weapon” (again), the US’ new casus belli was the need to aid regime change, built on the premise that the third round of negotiations did not yield an agreement — even as more talks were scheduled.However, with the attacks and Iranian responses now under way, it is clear that while Trump can still claim victory with Khamenei’s death, the regime surviving with new leadership (even if transitional) will be publicly verifiable evidence of the system’s resilience. It will represent change within the system, not of the system. Rather, having lost the Supreme Leader, Tehran has significantly fewer reasons to show restraint and more to follow through with its threat of massive retaliation. The Iranian threat of massive conventional retaliation to even a limited US strike, was intended to be a deterrent: to prevent the US attack. Iran could not afford to replicate its strategy from June 2025, when it retaliated symbolically to US strikes on Fordow, Natanz, and other nuclear sites by targeting Al Udeid air base in Qatar, given that it would puncture all Iranian deterrence. Washington was likely aware of this Iranian predicament. Combined with Trump’s fresh need for a decisive win (which a deal could no longer provide) and the commitment trap of the military build-up, this meant that the US strike could no longer be symbolic (as it could have earlier been, say around January).Story continues below this ad The aircraft carrier USS Gerald R. Ford in 2017. Washington began preparing for Iran’s massive retaliation, evident most prominently in that the USS Gerald R. Ford carrier strike group parked itself next to Israel. Photo: US Navy/Wikimedia CommonsNow, the US would need to attempt to draw maximum gains that airpower alone could provide, especially since boots on the ground remained a non-option. So, Washington also began preparing for Iran’s massive retaliation, evident most prominently in that the USS Gerald R. Ford carrier strike group parked itself next to Israel — not Iran — since Washington knew that Tehran would strike Israel in response. The US would rely on the wide gap in technological capabilities and the sophistication of its air defence network (enhanced by the Ford’s cover) to absorb Iran’s attacks.Also read | US and Israel have taken a dangerous gamble in Iran. It may backfireHowever, Iran’s retaliation has incorporated both vertical and horizontal escalation. Vertically, in terms of the use of missile/drone barrages that are intended to cause significant damage (unlike in June 2025), and horizontally in terms of the unprecedented across-the-board set of targets in the region, which includes attacks on Dubai, Bahrain, Riyadh, and Kuwait, targeting both military and civilian sites (where Tehran believes US servicemen to be sheltering). So far, the Iranian attack has comprised almost as many missiles and drones aimed at the UAE as at Israel. Iran has also combined this by announcing a halt to oil tankers passing through the Strait of Hormuz (a historic first), which brings 20% of global oil trade to a halt. Collectively, this reflects Iran’s desire to impose costs not only on the US and Israel, but also on regional states that host American bases and are Washington’s allies. With Khamenei’s death, Tehran (especially through the IRGC) has promised even fiercer attacks on US allies, especially Israel, and the military crisis is far from finished. However, the US-Israeli attacks have not brought forth organised coherent Iranian opposition to the fore, which can fight and replace the well-entrenched regime. This is in line with past precedent.Story continues below this adMoreover, striking civilian areas in Iran — including a school, which killed civilians including children — complicates the prospects of Trump’s call for systemic change in the country. As the war continues, the costs increase significantly for the US (since Trump does not desire a prolonged campaign) and Iran’s capacity to sustain its region-wide punishment is tested. But between the two, it is only Iran which is fighting for survival, which means it has far greater stakes in the conflict and consequently has more incentive to continue attacks until Washington backs down.