What are the implications of Trump's dramatic airstrike U-turn?

The non-interventionist has intervened.

The man who became US president based on his promise to focus on domestic priorities has plunged America into the Syrian civil war. And Donald Trump did so within his first 100 days in office.

It is simply a stunning policy reversal by the president. And we cannot know where this will end.

This was a significant step by the US. Yes, it was just 59 ship-launched cruise missiles aimed at a single target, the Shayrat airbase in Homs Province.

But once you enter the battlefield against President Assad there is no easy exit. America is now a player in the civil war.

If Assad commits further atrocities - whether by chemical weapons or by barrel bombs - does Trump order more strikes?

There are further questions as well. By weakening the Assad government, has the US inadvertently strengthened the Islamic State? Does Washington have a strategy to topple the Assad regime or was this just a one-off expression of moral outrage? How will Moscow respond?

This morning there are few easy answers.

But the most perplexing issue of all is how Donald Trump ever arrived at this point. Last year he repeatedly described potential US action in Syria against the Assad regime as a "terrible, terrible mistake".

Now Trump has become just the latest American president to intervene in the Middle East.

Over the next few days it is likely he will receive widespread domestic and international support for the military strikes.

The images of Syrian children choking to death on that Sarin nerve agent were deeply traumatic and they appear to have had a profound emotional impact on Trump, as they did on all civilised people.

The suspected chemical attack occurred on Tuesday in the northern Syrian town of Khan Sheikhoun.

But the reality is that on the complex Syrian battlefield very little will change. Assad will remain in power. The carnage will continue. And then the key question will return to haunt the White House.

What did the US strike actually achieve apart from sending a fleeting message to the world that there are limits to Trump's isolationist instincts?