President Donald Trump surprised the world by bombing the Syrian air base from which, he says, the horrifying chemical weapons attack on the town of Khan Sheikhoun was launched this week. All available evidence points to the Assad regime’s responsibility for that attack. Trump was personally highly upset by it, as he explained after seeing the shocking television footage of its aftermath. His move from that to order this missile strike demonstrates the policy flexibility he spoke of then. It also opens up a huge range of consequences – intended and unintended – in tackling the root causes of Syria’s six-year civil war.

Too rarely over those years have those with the capacity to curb the Assad regime’s brutality towards its own population, and the impunity and unassailability which go with it, actually done so. President Barack Obama refused to respond militarily in 2013 after a chemical atrocity which saw more fatalities; he justified that decision by defending the joint approach he adopted with Russia in removing and destroying Syria’s chemical armoury and cited US public opinion in support.

The Khan Sheikhoun attack suggests that achievement was not complete. And nor did the diplomatic engagement it showed possible bear fruit. Current efforts through the United Nations are at an impasse and are likely to be set back by these events.

In that perspective, this missile attack gives a clear symbolic signal to Assad – and to the Russians, Chinese and North Koreans too – of Trump’s willingness to use US military might. But given his determination to upstage Obama’s record at every turn and the rapidity with which he changed his administration’s stated policy towards the Syrian regime within the last week, he is open to charges of acting on a whim. An impulsive decision to assert US power would have enormous unintended and unforeseen consequences in this highly complex theatre of war.

Does moving within days from saying the Assad regime looks like remaining a reality to this blow against it, signify a strategic shift in the US position towards Assad’s regional Saudi Arabian and Sunni opponents and against Iranian and Russian support for the regime?

Has the hitherto articulated strategic imperative of defeating Islamic State by the Trump administration been made less primary? What of Trump’s expressed willingness to deal with Russia under Vladimir Putin? Or should this attack rather be understood as a once-off US warning about chemical – or nuclear – weapons?

Such questions demand an urgent response from the Trump administration in coming days. If they are left hanging, another unintended consequence will be to enhance the climate of uncertainty that fosters terrorist attacks like that in Stockholm yesterday or London two weeks ago.