Why the UK did not join the war on Iran?

The American-Israeli strikes on Iran have been widely compared to the 2003 war on Iraq. As ever, there are significant commonalities and major differences.
Back in 2003, it was the UK under Tony Blair that was the junior partner in an ill-advised, ill-conceived military adventure that lacked regional and international support. It was London that propped up an American president whose motives many did not trust. Many will argue that, as with Iraq in 2003, Iran in 2026 is not about weapons of mass destruction, not least as US President Donald Trump claimed that Iran’s nuclear program was “obliterated” by last June’s strikes.
This time, Prime Minister Keir Starmer has not just opted out, he has also seemingly denied the US the use of British military bases, including Diego Garcia in the Indian Ocean. Starmer on Saturday confirmed that the UK has had no role in the strikes. For Britain, this is less like Iraq in 2003 and more like Vietnam in the 1960s, when then-Prime Minister Harold Wilson refused to follow President Lyndon Johnson into war. Wilson and Johnson had arguably one of the worst relationships between the leaders of these two great allies in the post-Second World War era.
Many might have thought Starmer’s record in warmly engaging Trump would mean he was a dead cert to back the American action. This has been the UK’s role in recent decades. Prime ministers have feared jeopardizing what has been depicted as the single most vital economic, military and security relationship the country has. It was not just Blair who acted like this. For those who say David Cameron’s government did not back Barack Obama in 2013 over chemical weapons use in Syria, it was clear then that Obama was almost relieved that Parliament voted against military action and he used it as a way out.
So why the current British hesitation? It certainly does not emanate from sympathy for the Iranian regime.
Firstly, many in the British establishment share the fears of Middle Eastern leaderships: that this is an unnecessary, risky conflict. Starmer clearly would have preferred a negotiated diplomatic outcome and he issued a joint statement with France and Germany calling for the resumption of negotiations.
Secondly, many view this as an act of aggression, not something grounded in a necessity to fend off an immediate threat. What was Iran about to do that was so alarming as to lead to war? Its offensive capabilities had been seriously compromised. Iranian negotiators were engaging in detailed talks. These had made significant progress, as the Omani foreign minister explained in an interview on the eve of the US attacks. This means that many will view the war as illegal. Starmer, a former human rights lawyer, openly opposed the war on Iraq in 2003 as force was not authorized by the UN. 

Many might have thought Starmer’s record in engaging Trump would mean he was a dead cert to back the action.

Chris Doyle

Thirdly, since the raid on Venezuela in January and Trump’s threats to annex Greenland, Starmer has eased up on his close engagement with Trump. The UK did not join the Board of Peace. Starmer was also critical of Trump’s tariffs and angered by his comments about non-American NATO involvement in Afghanistan.
Fourthly, America’s European allies have been denied significant involvement in the Trump administration’s Iran strategy. In the past, the E3 (France, Germany and the UK) was involved in the nuclear talks. Trump ditched this. He runs things his own way. So, if the European military powers were to get involved in any offensive operations, would they have any degree of input or influence? This would be highly unlikely.
Fifthly, the UK would have had to participate alongside Israeli forces, which are still conducting a genocide in Gaza and effectively annexing the West Bank. The Israeli prime minister is wanted by the International Criminal Court for alleged war crimes and crimes against humanity. Few in Israel trust him, even those on the political right, let alone international leaders.
Finally, Starmer would be fully aware that the British public would not back a war on Iran. Opinion polls showed little enthusiasm for joining the strikes last June. Then again, even in the US, one poll published last week showed that only 27 percent of the American public supported an attack on Iran.
Starmer would also know that his Labour MPs would in all likelihood oppose UK involvement, so he would not win any vote in the House of Commons on a pro-war prospectus. He is not in the strong political position Blair was in 2003. He has just lost a by-election in Manchester to the Green Party and Labour looks as if it will be humiliated in May’s local elections. A war with Iran is just too risky for him.
This leaves the question of whether there is space left for Starmer to involve the UK in a more defensive capacity. British forces and assets are available to be deployed for protection. Starmer has confirmed that British planes are in the air in that role.
How will this affect relations with Washington? Much may depend on how the strikes unfold. If successful, Trump will happily take the plaudits. If they are a failure, reluctant allies like London may incur his long-term displeasure.

• Chris Doyle is director of the Council for Arab-British Understanding in London.
X: @Doylech