US sailors transfer ordnance on the flight deck of Nimitz-class aircraft carrier USS Abraham Lincoln, in the Arabian Sea, February 2026. US Central Command Public Affairs/Wikimedia Commons

US President Donald Trump’s bombing campaign against Iran, launched alongside Israel in February without the support of NATO allies, is a strategic gamble that appears to have been taken hastily and without clearly defined objectives. The war saw the assassination of Iran’s leader, the Ayatollah Ali Khamenei, on the first day of hostilities.

President Trump and his administration officials have offered shifting justifications for the war, including seeking regime change in Tehran and preventing the country from obtaining nuclear weapons. They have also highlighted a need to destroy Iran’s ability to attack the US and Israel, and to disrupt its support for regional proxy groups.

US Secretary of State Marco Rubio has also said that the US was aware that Israel was going to take action against Iran and therefore had to act ‘pre-emptively’, given that American forces were set to come under attack from Tehran.

International lawyers and national security experts say the American-Israeli attack highlights a significant lack of legal justification for the use of force and US presidential war powers. ‘The Trump administration has not put forward any information that Iran was imminently initiating hostilities,’ says Federica D’Alessandra, Co-Chair of the IBA Rule of Law Forum. ‘If you’re part of an original attack that is unlawful, then you don’t have grounds to claim self-defence. Further, the US failed to put forward public information that Iran had restarted a nuclear weapons programme.’

‘The idea of regime change as foreign policy flies in the face of something that we tried to put together in 1945, which the US was the major backer of and Trump is now breaking,’ says David Crane, a distinguished scholar in residence at Syracuse University and Founding Chief Prosecutor of the Special Court for Sierra Leone. ‘We have a unilateral decision to use force and an 80-year-old UN paradigm that actually does not authorise that.’

The Ayatollah Ali Khamenei was strongly criticised by a number of governments internationally and by Iranian opposition as a result of the repressive regime he oversaw. Crane says the ‘conundrum’ here is that ‘his removal is a laudable end state. It’s just [that] the means are questionable and illegal.’

In the first ten days of the war, about 1,800 people – both military and civilian, including 200 children – were reported killed, according to human rights activists in Iran. The Pentagon confirmed that seven US military personnel had been killed.

More than 100,000 people had been forced to flee Tehran, according to the UN Human Rights Council, citing local estimates. In southern Lebanon, hundreds of thousands of civilians have left their homes in the face of Israeli attacks targeting the Iran-backed group Hezbollah. Tens of thousands of foreign nationals were leaving the region.

Pete Hegseth, the US Defense Secretary, said in early March that the US military would continue bombing ‘without mercy’. President Trump demanded Iran’s ‘unconditional surrender’ via social media on 6 March, adding that his country would work ‘to bring Iran back from the brink of destruction’ once a new leader acceptable to the US is chosen.

President Trump’s ‘idea of diplomacy is that he sends over a set of demands, and he expects the other side to capitulate to them,’ says Adam Weinstein, Deputy Director of the Middle East programme at the Quincy Institute for Responsible Statecraft in Washington, DC.

Weinstein believes the Trump administration doesn’t have an ‘end state’ in mind for the war. ‘If you listen to the Trump administration officials, the reasons keep changing,’ he says. ‘First, they want to destroy the missile capacity. Then they say it’s because Israel was going to attack anyway. Now, [President Trump is] saying that he wants a part in choosing the next leader of Iran.’ Weinstein adds that the Trump administration continues to update the timeline for the conflict, ‘from days, to weeks, to months.’

Domestically, President Trump appears to have been aiming for a quick political victory similar to the capture of President Nicolás Maduro from Venezuela in January. But the attack on Iran is proving controversial.

Following the US wars in Afghanistan and Iraq launched after the 2001 al-Qaeda attacks, many Americans are sceptical of using military force to reshape the Middle East. Early polls show a majority of Americans disapprove of President Trump’s military action in Iran.

After the war began, opposition Democrats forced votes in Congress that would have curtailed President Trump’s authority to continue the bombing. The resolutions failed narrowly along partisan lines but aren’t the end of the process. Congress still holds a lot of sway. The US Constitution vests warmaking authority with the legislature and a 1973 War Powers Resolution provides tools to hold presidents to account.

Under the law, once the president introduces US forces into hostilities, the military action must end within 60 days unless Congress authorises or extends the deadline. President Trump will probably dispute the applicability of this rule, which may set up a confrontation with Congress if the war is still ongoing. In the past, judiciary have been reluctant to intervene in War Powers conflicts between the legislative and executive branches of government.

A change in leadership in Congress following November’s midterm elections would be likely to see limits placed on funding for the military operation. A new Congress could conduct oversight investigations into President Trump’s decision to launch the attack, the intelligence provided and what coordination took place with Israel and other allies. Those hearings could produce significant consequences for President Trump and his administration.