President Donald Trump has now twice shown
that he will reinforce the red line against the use of chemical weapons, which like all weapons of mass destruction are banned under international law.
Russia is also a signatory to that law. Even Syria joined in 2013, when it staved off threats of a previous strike by pledging to disarm its stockpiles of chemical weapons.
Now as the allies make their bomb damage assessment, it's worth recalling what the former head of Britain's MI6 told me as the action was being prepared.
"I think is quite important because there have been a series of Russian actions against which the West has pushed back ... ," Sawers said.
Referring to the poisoning of an ex-Russian spy in England, he said, "(In) the Skripal case
... I think the Russians were surprised that it wasn't just Britain that responded, but there were 26 countries as well as the NATO headquarters that had expelled Russian intelligence officers, and the United States has taken action in response to Russian meddling in the US elections with a whole series of sanctions against oligarchs and Russian companies.
"And we're announcing this action is Syria. Now, this isn't part of a concerted plot against Russia, but the Russians might see it that way. So, one thing which is really important here is clarity of communication to the Russians about what this is about. We had that during the Cold War. It's decayed a bit frankly over the last 20 years."
Indeed, communications have decayed so badly that UN Secretary-General Antonio Guterres said Friday at the UN Security Council that "the Cold War is back -- with a vengeance, but with a difference. The mechanisms and the safeguards to manage the risks of escalation that existed in the past no longer seem to be present."
The US-led alliance insists it deliberately avoided targets that could harm any Russians on the ground in Syria and that the military "deconfliction channel" was used.
These strikes can also be seen as part of a military process that began in the summer and fall of 2014 when the United States and many allies started a sustained campaign to bomb ISIS targets in Iraq and Syria.
They continue to say the current military action is not aimed at toppling Assad or taking sides in the civil war.
Regarding the risk of getting into an accidental war with Russia -- it is again worth recalling the recent past: that accidents do happen, and they do not necessarily lead to a shooting war between major powers.
As CIA Director Mike Pompeo said in his confirmation hearings to become secretary of state this week
, a lot of Russians were killed by US forces
on the ground in Syria in February: He told Congress that "in Syria, now a handful of weeks ago, the Russians met their match. A couple hundred Russians were killed." (They were reported to be military contractors, not Russian government troops.)
But this did not lead to any retaliation against the United States.
Even further back, in 1999, NATO accidentally bombed the Chinese Embassy in Belgrade during its humanitarian intervention in Kosovo. Again, this terrible accident did not lead to military conflict between Beijing and Washington.
But where to now in Syria? Russia and Syria blame Israel
for a barrage of missiles at a Syria base after the suspected chemical attack last week in Douma, and the former commander of the Israeli air force, Maj. Gen. Eitan Ben Eliyahu, told me this week that to really cripple Assad's chemical weapons ability, a sustained military effort is necessary. "We can continue and we do that. But with a very close support from the United States, we can launch more and more and more (attacks)."
When I asked him if he agreed with analysts who said all Syria's airfields should be taken out, he gave this clear answer: "Well, yes, I do. I certainly do."
That is unlikely to happen, at least now. But Trump and President Emmanuel Macron of France have said there will be more if Assad uses chemical weapons again.
In the meantime, the only way a military campaign can have a lasting impact is if it is part of a wider diplomatic and political strategy.
As former US Secretary of State Madeleine Albright told me: "I am not just for using military force. I think that we need to look at the full spectrum of tools.
"I think that the sanctions that have finally been put on need to be really enforced. I do think, there (needs) to be diplomatic contact," said Albright, having been central to the Clinton administration's muscular diplomacy to end wars in Bosnia and Kosovo in the 1990s.
"And what is the long term here because frankly, I don't think there's any solution in Syria unless there is a political settlement of some kind, where the various parties are involved, and where there's a plan for what the next steps are."
About a one-off military action, Albright added: "The problem has been, this kind of immediate gratification on something, and what we need to do is to have a longer term (view), and it has to involve that combination of tools."