Trump’s Iran war aims are far from clear – but the UK cannot afford to use international law as an alibi
Keir Starmer gives an update on the latest situation in the Middle East, March 2026 (Alamy Live News)
4 min read
Scarred by Vietnam, General Colin Powell, chairman of the joint chiefs during the first Iraq war and secretary of state during the second, set three tests for committing the United States military: a clear goal; a clear exit strategy; and overwhelming force.
President Trump’s campaign against Iran meets none of those tests. Even Republicans are worried that there is no consistently articulated definition of success. The forces Trump has deployed are formidable but not enough to overthrow the Iranian regime and then stabilise a country of 90 million people. And exit strategies, in this region, are usually determined by enemies with more strategic patience. As the Taliban warned: “You have the watches. We have the time”.
Iran’s strategic doctrine is not to contest a conventional war but fight a prolonged campaign of resistance through asymmetric action – drone strikes against civilian targets, assassinations, terrorist attacks – by both their own forces and proxies like Hezbollah and the Houthis.
And Britain? We’ve chosen not to influence the outcome
When I was UK national security adviser, we developed the Fusion Doctrine for such situations and asked ourselves what outcomes were likely and what we could tolerate: the reasonable best and worst cases, and the minimum acceptable. We nicknamed them “The Good. The Bad. And the Ugly”.
Applied to Iran, that analysis is uncomfortable. The best outcome would be the replacement of the theocratic dictatorship with a pluralistic, representative government. Iran has genuine democratic instincts. Whenever the people have been given any kind of say, they have chosen the most progressive option. But the country is ethnically fractured, and the regime’s toughest elements are dug in. The conditions for a smooth transition to democracy do not currently exist. Iraq and Afghanistan are cautionary tales.
The worst outcome would be collapse into anarchy and civil war. Syria and Iraq both demonstrated what happens when a multi-ethnic, multi-confessional state loses its centre of gravity. And Iran’s neighbours – notably Turkey, Russia, Iraq, Pakistan – each have vital but competing interests. The likelihood of refugee flows, proxy warfare, narcotics and nuclear material in unknown hands should concentrate minds from Washington to Beijing.
That leaves the Ugly – the Venezuela option. Despite some regime-change rhetoric, Trump has signalled that he could live with a chastened post-Khamenei regime: nuclear and ballistic missile programmes destroyed, proxies curtailed. This would settle the isolationist wing of the Maga base and calm energy markets rattled by a campaign started without first restocking the strategic petroleum reserve. The Gulf states could accept it too: their concern has always been Iranian projection, not Iranian governance. The potential outlier is Netanyahu, who might calculate that an Iran in chaos serves Israel better than a defanged but resentful adversary.
And Britain? We’ve chosen not to influence the outcome. So, our core national interest is in protecting our citizens today and protecting the state of our alliances the day after. The contrast with 2003 is instructive. George W Bush – not Tony Blair – decided to invade Iraq. But, in contrast to his predecessors over Suez and Vietnam, Blair decided that alignment with the US was Britain’s overriding national interest. While their support has been political not operational, Canada and Australia have chosen that path this time. The UK has not.
In Washington, it isn’t just President Trump who resents the government’s position over the lawfulness of the US strikes, the initial denial of access to our military bases and the subsequent limitations on their use. Others there are already asking whether a direct arrangement with Mauritius for access to Diego Garcia might be better for the US than the constraints they have to negotiate with the UK. And while our regional allies are doubtless grateful for the defensive contribution we are making against Iranian missiles and drones, as attacks intensify, they are asking whether the British response has been resolute enough.
The government faces a genuine tension between an anti-war, anti-Trump constituency and the responsibility to engage robustly with national security that stretches back to Attlee and Bevin, and which the Prime Minister has displayed so consistently over Ukraine. What conclusions will our allies draw? Or our adversaries? International law is a framework of legitimacy. It must not become an alibi for inaction against dangerous regimes in the ugly world we now inhabit.
Lord Sedwill is a crossbench peer and former UK national security adviser
