What US strike on Syria represents
The fast & aggressive retaliation against the chemical attack may lead to a 'Trump doctrine' on foreign policy intervention
When US President Donald Trump took office less than three months ago, few would have predicted he would find himself so quickly launching military strikes against Syria.
Since January, his administration has been quietly reducing support for Syria's rebels, seemingly opening the door for an eventual settlement that might leave Syrian President Bashar al-Assad in charge.
None of that was necessarily changed by Thursday's (US time) missile strikes against the air base believed to be responsible for a suspected nerve gas attack barely 72 hours earlier.
In taking such aggressive action so quickly, however, Mr Trump sent what he sees as a robust message of US resolve - not just to Damascus but also other potential US opponents, including Russia, China and, most particularly, North Korea.
Some kind of action was probably inevitable. Had Mr Barack Obama still been in the White House, he might have taken a similar step.
The Russia-brokered deal that averted US military action after a 2013 chemical strike near Damascus was, after all, predicated on Syria giving up its poison gas stockpiles.
The government in Damascus conducted handovers of what it said was all of its chemical stocks, and signed the Chemical Weapons Convention. Such an egregious and unmistakable breach of that deal was going to have to be punished.
But the speed with which Mr Trump ordered the strikes does seem to be a shift from the Obama administration, which often discussed such actions openly in advance.
In hitting just a single air base, the overnight strikes were also much more limited than the military action Washington was considering after the 2013 chemical attack - that likely involved an overwhelming assault on Syrian air defences and other facilities, an action deliberately designed to undermine Mr Assad's grip on power but not enough to topple him.
While Thursday's missile strikes infuriated Russia, which compared them to the 2003 invasion of Iraq, the US appears to have been careful to avoid inflicting any casualties on Russian forces in Syria.
That was in dramatic contrast to some of the plans a potential Hillary Clinton administration was said to have been considering - they included imposing "no-fly zones" that could have seen US jets shooting down Russian aircraft.
The first question now is what this means for the US policy towards Syria.
In the run up to last week's chemical strike, both US Secretary of State Rex Tillerson and Defence Secretary James Mattis suggested that Washington no longer regarded Mr Assad's removal as a priority. It remains to be seen if that is still the case.
It is certainly possible that the Trump administration could shift back towards the approach taken by its predecessor, supporting rebel groups and doing what it can to undermine those in charge in Damascus.
For now, however, that seems relatively unlikely - the Trump administration has made it clear that its main priority in Syria continues to be tackling the Islamic State in Iraq and Syria, with an assault gradually looming on that group's de facto capital of Raqqa.
Most importantly, the US still has no credible way of bringing down Mr Assad, should it wish to do so.
It has no appetite for a troop-heavy intervention, and Mr Trump has repeatedly stressed that he believes the lessons of Iraq and Libya are that removing regional strongmen is often a bad idea.
The most important lasting effect when it comes to geopolitics, however, may be on US-Russia relations.
It is unclear if Moscow had advance knowledge of the chemical strike, but it certainly is angry at the US actions since.
That sends a stark message that the Trump administration may take a tougher line with Moscow despite - or perhaps, in part as a result of - the ongoing suggestions that Russia intervened in the US election to try to help Mr Trump.
That may also be a sign of shifting sands in Washington.
This week saw presidential adviser Steve Bannon's dismissal from the White House National Security Council.
Mr Bannon's ousting is already seen to have strengthened the hand of the newly appointed National Security Adviser, Lieutenant General H.R. McMaster.
Thursday's strike may be the clearest sign so far of the "McMaster-isation" of the Trump foreign policy: well-defined and limited-but-decisive action with a relative clear and simple goal.
At worst, though, critics are describing it as yet another sign of the President's impulsive behaviour, a "shoot first and ask questions later" approach.
Either way, if there is to be a "Trump doctrine" for foreign policy intervention, last Thursday's missile strikes will almost certainly be seen as the start of it.
For now at least, this strike seems to have been a limited punishment, not the start of another US-backed Middle East regime change.
The writer is Reuters' global affairs columnist, writing on international affairs, globalisation, conflict and other issues.