The death or downfall of a regime figurehead is often an awesome and magisterial but terrifying event. Those living through the demise of Charles I of England (beheaded in 1649), the execution of Louis XVI of France in 1793, Napoleon’s final defeat and exile in 1815, the massacre of the Romanov dynasty in 1918, the abdication of the German Kaiser later that same year, Adolf Hitler’s suicide in 1945, and, more recently, the grisly fate of Saddam Hussein and Muammar Gaddafi in Iraq and Libya, were in no doubt as to the gravity of the moment. Along with relief that a nightmare had ended, foremost in most minds was a fearful, ‘what happens next?’

Such confused emotions were expressed, according to an observer of the demise of Charles I, as ‘a moan as I never heard before and desire I may never hear again [that] rose from the assembled crowd’. Transitions of power can be peaceful, as seen with the deaths of General Francisco Franco of Spain in 1975, or Marshal Tito of Yugoslavia in 1980 (at least for a while), but foresight on this matter is rare for autocrats and dictators. The likes of Vladimir Putin, who has no public succession plan or underlying unifying doctrine, are wary of engineering their own doom at the hands of an appointed stand-in.

So, on one level, it must seem bewildering to those waking up in Iran this morning, where the country’s opaque leadership has just confirmed the deaths of Supreme Leader, Ayatollah Ali Khamanei, along with his daughter, son-in-law, and grandson. Several of his Shia henchmen also perished, including his son, Mojtaba, and Islamic Guard commander, Mohammad Pakpour. In the streets of Tehran and elsewhere, there will be much rejoicing by proud Persians, tinged with anxiety as to their future. Observers as well as citizens are puzzling over the conundrum of whether Iran remains a state run by the Islamic Revolutionary Guard Corps (IRGC), as that armed bunch of fanatics continue to fling missiles at Iran’s neighbours.

The Israeli-American military onslaught of 28 February illustrated how isolated Iran had become; its Chinese and Russian allies sat on their hands and whistled. While the late Supreme Leader’s predecessor, Ayatollah Ruhollah Khomeini, was the ideological force behind the revolution that ended the rule of the Pahlavi monarchy, Khamenei was different. He shaped Iran’s military and paramilitary architecture, which controlled the state and projected force outside it. From 1989, the 86-year-old leader had followed in the footsteps of Khomeini in using his state to sponsor international terrorism, but rarely employed raw combat power directly. After 37 years at the top, Khamenei had lapsed into otherworldliness; he blasted his attackers with impressive rhetoric, but had no practical military strategy to offer. That is now in the hands of his surviving minions, who are assessing their options while continuing the fight.

Incredibly, by firing munitions at all of its neighbours during Saturday and Sunday, the IRGC has managed to unite Jordan and the Arab Gulf states of Bahrain, Kuwait, Qatar, UAE and Saudi Arabia, who are not always the best of friends with one another, never mind Israel, against Tehran. Oman is particularly annoyed, given that it hosted mediation talks in Geneva as recently as last week, yet was nonetheless obliged to intercept Iranian missiles aimed at its territory. Meanwhile, outsiders are teasing out the implications of another nail in the coffin of the rules-based order, which ran the world after 1945.

Since the Second World War, international law, less a rule book than a series of mutually agreed conventions grafted onto deliberations and treaties made earlier in the Hague and at Geneva, has enshrined the centuries-old principles of non-interference in the affairs of other nations, and the illegality of unprovoked invasions. These, in turn, absorbed the ideas of justice and injustice in war found in the works of St Thomas Aquinas, and later the Treaty of Westphalia of 1648.

However, Trump’s decision to go to war with Iran without any attempt to gain international consensus at the UN or anywhere else, or even gain the approval of his own Congress, adds to a set of recent examples of the technically illegal use of force to achieve foreign policy goals. Russia may feel retrospectively justified in its illegal invasion of Ukraine, while Beijing is watching closely in respect to any military action it may take against Taiwan. ‘We are in an era of great power politics and this is what it looks like,’ says Rob Johnson, the head of the Changing Character of War Centre at Oxford University.

It seems as though President Trump has shelved his Board of Peace, established at the World Economic Forum on 22 January 2026 as an alternative United Nations. A month later, and seemingly bored of peace, he has gone to war. The warning signs were there in the form of the build-up of carrier battle groups and other signatures of combat power, but Omani-led diplomacy in Geneva seemed to be making progress. Then, it exploded onto our screens in a day of reporters clad in body armour and helmets, bearing mobile phones, and chirruping air-raid alerts. Operational code names often hint at underlying reasons for military action. The current operation against Iran is called ‘Lion’s Roar’ by Israel – a successor to the ‘Rising Lions’ airborne attacks of 12-24 June 2025 – and ‘Epic Fury’ by the US. This is because Trump is furious with the Tehran regime for not doing a deal with him over its nuclear capability. Talks over Iran’s ballistic and nuclear aspirations were ongoing in Geneva as recently as Friday. Oman’s foreign minister, shepherding the Iran-American talks, appeared stunned.

Trump’s robust declaration of ‘major combat operations’ (his euphemism for war) on domestic television, listed 47 years of humiliating attacks on US forces, and his determination that Iran will never possess a nuclear weapon. Rapidly burning up international diplomatic goodwill, he has made no effort to form a coalition of western or other regional players, all of whom are nervous of regional destabilisation. He has since spoken to calm the fears of regional leaders and the Secretary-General of NATO, Mark Rutte. The UK has issued a balanced statement of support, but confirmed its bases were not used and that it will not take a military part in the strife, although RAF jets are airborne in a protective role. If the campaign is prolonged, however, US forces will need access to British military infrastructure.

For America, this a high-risk strategy. President Trump has been emboldened by his successful action in Venezuela, but Iran is not Venezuela. Far more military effort will be required to subdue this potent adversary of over 600,000 square miles, housing a population of 90 million, and which has many covert allies across the Middle East. Any of them could mine the sea lanes, paralysing the movement of oil tankers, swarm naval vessels with suicide drones, conduct sabotage, initiate vehicle bombs and assassinations using sleeper cells. Iran was in conversation with China about acquiring powerful anti-ship missiles, but events have overtaken this aspiration. The Strait of Hormuz, through which a fifth of the world’s oil passes, is in danger of closure. Shipping, insurance and oil prices may climb steeply in the short term, as will gold, always a safe haven in times of tension.

American lawmakers will be anxious that Congress, let alone the UN, has not debated this move, nor were either even consulted. It is significant that the president’s war room is not in the White House, but at Mar-a-Largo, and his announcement was not accompanied by the usual array of be-medalled admirals and generals. Missing, for example, was General Dan Caine, the current Chairman of the Joint Chiefs of Staff, suggesting this was Trump’s own initiative, and made despite military advice to the contrary.

Although Australia is supportive, questions are being asked at the United Nations by Spain and France about the legality of this pre-emptive strike. Democrats will be suspicious that this is a distraction from the domestic crisis of ICE raids on immigrants and rumblings over the Epstein files. The action may split Trump’s MAGA-America First base, many of whom remain resolutely isolationist, and who may assess that Israel pushed their ally into war. Iran, of course, is sworn to Israel’s destruction. Not least because of the 7 October 2023 attacks, Israel interprets this in terms of an existential war to the death. So does Iran.

The stakes for America are different. This is not a necessary war, or one to fight to the death for Washington. Trump’s boast of ‘solving eight wars’ will be compromised by starting a major new one. Therefore, the president needs a swift conclusion, rather than a regional Vietnam-type forever conflict. In his presidential address, he warned his nation to prepare for casualties, leaving some suspicious as to how far Trump will push his war. Overriding substantial objections from the Pentagon, he has chosen the most dramatic of a range of options presented to him by civilian advisers, who concluded that Iran’s military power and that of its Hezbollah, Hamas and Houthi proxies is degraded.

In the UK, Prime Minister Starmer went into a COBR (Cabinet Office Briefing Room, pronounced ‘cobra’) conference, perhaps indicating he has not been consulted. His party may dislike the rule of the mullahs in Tehran, but, following Tony Blair’s intervention in Iraq in 2003, Labour would find it near-impossible to back any military support of US forces in Iran. The so-called E3 (France, Germany and the UK) issued a joint call for ‘regional stability’ and condemned Iran’s strikes in the Middle East. Domestic political divides over the US-Israeli strikes will surely play out in opposing protests on Britain’s streets, just as the streets of Baghdad, Karachi and Istanbul are currently echoing to pro-Shia demonstrations in support of the Islamic Republic, some violent, and others supporting the Sunnis of the region.

It is difficult to understand what US and Israeli airpower can achieve alone, without boots on the ground. I am old enough to recall the distinguished American war professor, Theodore Reed ‘T. R.’ Fehrenbach, teaching my group in a military academy: ‘You may fly over a land forever; you may bomb it, atomize it, pulverize it and wipe it clean of life – but if you desire to defend it, protect it, and keep it for civilization, you must do this on the ground, the way the Roman legions did, by putting your young men into the mud.’ Airpower has never achieved a decisive result without the use or threat of use (as in Kosovo in 1999) of land power.

The current methodology of air attacks doesn’t match the end state of regime change. However, a replacement regime is not ready and waiting in the wings, even if Reza Pahlavi, son of the last Shah, is impatiently kicking his heels in the United States. Unless the IRGC magically and suddenly collapses, success may take months, time which might be available to Israel but not to the US, whose combat power is more vulnerable, based on the Abraham Lincoln and Gerald R. Ford carrier support groups at sea. They carry about two weeks’ supply of munitions with them, but both need extensive logistical support. Trump will need a clear military result by 3 November, the date of the US mid-term elections, when contests for seats in the House of Representatives and Senate will be interpreted in terms of his policies.

The Prussian war theorist Carl von Clausewitiz would remind Trump and Netanyahu that wars rarely unfold as the initiators anticipate. Trump’s invitation to Iranians to ‘seize control of your destiny’ feels too late. His bombastic appeal for the fanatics of the IRGC to ‘lay down your arms or face certain death’ will be ignored. Trump is light on detail. Who will accept the surrender of the IRGC, or run Iran after the Ayatollahs? Rather like Hitler’s SS in 1945, Iran’s loyalist fanatics may continue to fight beyond all logic, and believing they have already been pushed into a corner, will welcome martyrdom.

Many observers across the world are torn between wishing the end of the Islamic Republic’s brutal regime, and wanting any kinetic action to be conducted within the rules of war. We are in the early moments of a potentially very serious conflict, whose end-state is difficult to visualise. I’m not sure Trump will shed any tears over the fact that his action was technically illegal, if he was even aware of that in the first place. Make no mistake, the world needs to be rid of the mullahs’ regime in Iran. Their demise will, in one way, make the world a safer place. Yet, at the same time, the epoch of the rules-based order may really be over. If so, I shall mourn its passing and fear for the future.