Donald Trump’s professed change of mind about Syria and its president Bashar al-Assad – and his hints of possible punitive action in response to Tuesday’s chemical attack – have underlined his administration’s volatility on the world stage.

The suggestion that the US could intervene in the conflict would be a radical departure from the exclusively “America first” approach that has hitherto defined Trump’s policy. In Syria, that meant focusing exclusively on Islamic State (Isis) and other extremists, and putting off dealing with the country’s political transition.

“I don’t like Assad at all,’’ Trump declared in a presidential debate last October. “But Assad is killing Isis. Russia is killing Isis and Iran is killing Isis.”

Only a few days ago, the US ambassador to the UN, Nikki Haley, declared: “our priority is no longer to sit and focus on getting Assad out”. Secretary of State Rex Tillerson had argued the Syrian president’s future “will be decided by the Syrian people”, ignoring the fact that many of those people were under relentless bombardment by Assad and unable to voice an opinion.

Even more confounding was Trump’s declaration that the Idlib gas attack crossed “many, many lines – beyond a red line”. The comment came only hours after the president had lambasted Barack Obama for laying down the original red line on Assad’s use of chemical weapons in 2012 and then not attacking when the line was crossed in August 2013.

Trump has consistently argued that the failure to deliver on the “red line” threat projected US weakness. But it was far from clear on Wednesday what action his own administration would take now that Assad had crossed “many, many lines”.

But there were plenty of hints that the administration was at least considering a direct – possibly military – response.

Haley said that when the UN fails in its duty, “there are times in the life of states when we are compelled to take our own actions”. The White House spokesman, Sean Spicer, said on Tuesday: “Rest assured that I think [Trump] has been speaking with his national security team this morning, and we will continue to have that discussion both internally with our national security team, as well as with our allies around the globe.”

The defence secretary, James Mattis, said the Idlib act was “a heinous act and will be treated as such”.

The national security council that Trump consults will now be shorn of his chief strategist, Steve Bannon, a white nationalist who has been the main advocate of the view that the struggle to destroy “radical Islamic terrorism” justified alliances with the likes of Assad and Vladimir Putin.

Bannon’s departure is a win for the national security adviser, HR McMaster, who rejects the use of the term “radical Islamic terrorism” and its implications for analysis and policy. McMaster, an ally of Mattis, is now likely to have a much freer hand in formulating Syria policy.



However, these veteran military leaders will face the same constraints as the Obama administration when it comes to considering US options. Any punitive strike would have to be backed up by consideration on what to do the day after, if Assad and Putin ignore the message. Increasing military aid to rebels would carry the same risk of falling into the hands of extremists.

Nor has any policymaker on the left or right ever credibly articulated a plan for Syria should the US succeed in toppling Assad, a strategic vacuum reminiscent of the disastrous Iraq occupation.

Moreover, any action against the Syrian regime would now also be against Russia.

Colin Kahl, a former member of the Obama White House, noted in a tweet that it was “worth remembering there are Russian advisers at nearly every relevant Assad base. Any strike means dead Russians.”

The Idlib attack appears to have driven the first meaningful wedge between Trump and Putin. He told the New York Times: “I think it’s a very sad day for Russia because they’re aligned, and in this case, all information points to Syria that they did this.”

Meanwhile, Haley – presumably with White House approval – delivered a scathing indictment of Russia at the UN Security Council.

The shift in mood is clearly another consequence of the Idlib atrocity, but it is too early to say how lasting that shift will be and whether it could lead to the US and Russia clashing in the Syrian battlefield.

The depth and duration of the change is particularly hard to predict, as it appears to have been driven by Trump’s immediate emotional response to the event.

In his remarks in the Rose Garden, he referred repeatedly to the children and babies who had been killed.

Yet the victims of the Idlib attack are far from the first Syrian children to have suffered at the hands of the Assad regime, with Russian and Iranian backing.

And there has been substantial evidence of previous regime use of chemical weapons. What seems to have made the difference this time is that Trump spent some time looking at pictures of the aftermath.

The attack had a “big impact” on him and his “attitude toward Syria and Assad has changed very much”.

The policy implications for his change in attitude are far from clear. The president’s outlook could revert to its default mode once the images fade in his mind.

But it seems clear that Assad may have misjudged Trump. In November, the Syrian leader called him a “natural ally”, perhaps seeing in him a ruthless strongman like Putin and himself.

The reality now seems to be more complicated, emotional – and unpredictable.