(CNN)The last time President Bashar al-Assad appeared to turn chemical weapons on Syria's civilians, the US President blinked. Assad crossed President Barack Obama's red line without consequence.
Analysis: Why diplomacy stopped working in Syria
This time, America's new President, Donald Trump, says he won't look the other way. That he is horrified how "beautiful little babies" have been killed by chemical weapons that are "so lethal."
But will the world now look to the US for leadership in putting an end to Assad's slaughter?
The answer, for many reasons, is possibly not.
President Trump has hardly set himself up as the ally you need in a tight spot. It's still far from clear to his traditional allies if he means what he says. He has, to say the least, been both contrary and contradictory.
His pronouncements on a number of international issues -- be it on the EU, Brexit, NATO, Russia, China and North Korea -- have weakened confidence and raised concerns that the US may not be the friend to many that it once was.
Until last week, the closest his administration had come to articulating a policy on Assad was Secretary of Defence James Mattis saying " ... on the Assad issue, we are working on this one day at a time as we throw Daesh [ISIS] on to the back foot," and Secretary of State Rex Tillerson saying "I think the status and the longer-term status of President Assad will be decided by the Syrian people".
Trump's response to Assad's apparent attack this week is likely to erode the confidence of allies further. In the immediate aftermath he said: "These heinous actions by the Bashar al-Assad regime are a consequence of the past administration's weakness and irresolution. President Obama said in 2012 that he would establish a 'red line' against the use of chemical weapons and then did nothing."
Then, On Wednesday, he appeared in the White House Rose Garden beside Jordan's King Abdullah, suggesting that he might take unspecified action against Assad: "I now have responsibility, and I will have that responsibility and carry it very proudly ... These heinous actions by the Assad regime cannot be tolerated."
In the aftermath of Tuesday's horrific scenes, the UN rushed to gather leading diplomats to debate the outrage. Few expect that the outcome of their talks will amount to more than the usual handwringing -- as has been the case ever since Obama failed to enforce his "red line."
The vacuum created by the Obama administration's lack of action in Syria allowed Russia to take control of the conflict. Now, Russian President Vladimir Putin dominates the international agenda on Syria. His forces tip the military balance both in the sky and on the ground.
It was Russia that arranged the recent peace talks in Kazakhstan and increasingly, in America's absence, has had greater behind-the-scenes heft at UN peace discussions.
Indeed, Russia has already rushed to Assad's defense with an implausible smoke screen story that the Syrian air force bombed a "terrorist" chemical weapons facility, resulting in the release of the toxic gases. As long as Russia sticks to this line, a unified international response on Assad is impossible.
Meanwhile, international outrage and indignation has been piling up. António Guterres, the UN Secretary General, while attending EU talks in Brussels aimed at alleviating the suffering inside Syria said: "The horrific events of yesterday demonstrate unfortunately that war crimes are going on in Syria and that international humanitarian law (is) being violated frequently."
The EU talks themselves, coming as they do after years of conflict which has led to hundreds of thousands being killed and millions forced from their homes, is a reminder that international resolve these days amounts to little more than picking up the pieces after a disaster.
France has called on Guterres to bring world powers to the table at the UN. Just last week at a NATO foreign minister's meeting in Brussels, France's foreign minister appeared critical of Trump's position on Assad, demanding that Rex Tillerson provide more details of the recently revealed US ambivalence to Assad's continuing authority.
Whatever coalition of the willing may have existed, it is clearly fraying.
Britain's Foreign Secretary Boris Johnson added his outrage to the mix: "All the evidence I have seen suggests that it was the Assad regime who did it in a full knowledge they were using illegal weapons in a barbaric attack on their own people. I would like to see those culpable pay a price for what they have done and I certainly cannot see how a government like that could continue to have any kind of legitimate administration over the people of Syria."
Johnson, perhaps by virtue of Britain's "special relationship" with the US, will be more acutely aware than most of how unready they are to face down Assad.
Trump's campaign, in part, was built on the bullish rhetoric of bombing ISIS out of existence.
His speeches rarely, if ever, broadened out to Syria and Assad. Indeed, his early warmth toward Russian President Vladimir Putin, whose forces side with Assad, seemed to hint that Assad could get some kind of free pass, as long as ISIS was crushed.
In the wake of yesterday's attack, the US is proposing a UN resolution. It is redolent with language we have become used to when talking about Syria. It condemns, expresses, recalls, emphasizes and requests, but in no place does it demand or insist.
Equally unclear was US ambassador to the UN Nikki Haley's statement that "when the UN consistently fails in its duty to act collectively there are times in the life of states that we are compelled to take our own actions".
Yet again, the international community will likely gum away at the issue.
"Jaw jaw," British PM Theresa May said earlier this week -- quoting Winston Churchill this week, albeit on an entirely separate issue -- is better than "war war."
But in the case of Syria, until the UN shows and uses its teeth, Assad and Russia's war will continue spewing carnage.
To lay responsibility for the horrors in Syria and the response to them at Trump's door may be misplaced, although it's hard to overlook that this attack came less than a week after the White House backed away from the previous US policy of demanding that Assad must go.
The manner in which Trump's predecessor handled the last major Syria chemical attack came to define his international legacy: Obama was weak when put to the test.
This reinforces White House spokesman Sean Spicer's assertion last week that Trump has been left a weak hand on Syria. But how astutely Trump plays the few cards he has in this unfolding crisis may come to define his own overseas legacy.
After the comments Trump made standing next to King Abdullah, Assad will be wondering if Trump has set him a new red line, and if so how far he can push it.
Trump's allies will be worrying that the new president may have already wrong-footed himself .