By chief foreign correspondent Philip Williams.
It happened overnight.
One day Bashir al-Assad was part of the solution. An odious but necessary partner in the battle against Islamic State.
Then the gas attack in Khan Sheikhoun.
US President Donald Trump had changed his mind. A deal with the devil was no longer possible. Lines had been crossed, the regime was now going to pay.
The strike was as surgical as technology enables from a distance. Specific parts of one military airfield were destroyed.
This was a very direct act of controlled aggression with a clear note attached. Chemical weapons are out.
Use them again and expect a visit from a Tomahawk missile on your headquarters, palace, anywhere you value.
But does it in itself remove the man blamed for the atrocity at Khan Sheikhoun, President Bashar al-Assad?
If this is to be the "game-changer", the beginning of the end for the Syrian leader, it will take a lot more than a few missiles to dislodge him.
As long as the Russians support their Syrian proxy, he will remain.
That is unless Mr Trump decides to take on not just the Syrian President, but Vladimir Putin too. That is unlikely but not impossible.
Or that the Russians could decide it's all too hard and dangerous and strike a deal with the Americans.
How that could be achieved and save face on both sides is hard to see.
In effect, the Americans have declared war on the Syrian state, or what remains of it.
What happens if the Syrians try and shoot down US, or even Australian aircraft on their bombing runs against Islamic State over Syrian skies?
While the Russians and Americans have carefully avoided any potential "accident" in Syria via a hotline, that choreography could come crashing down with all the risks of escalation attached to it.
And if the Syrian President was removed or persuaded to go, what then? There is no alternative government structure to take over.
In areas not under government control, the power vacuum has been filled by a myriad of groups from Islamic extremists to civilians turned fighters who dared to dream of a democratic and free society way back in 2011.
It would require a massive peacekeeping force, the likes of which the world has never seen, to impose a sustainable new order.