In the last few days, President Barack Obama has lurched from diplomatic caution to military bellicosity over what to do about the Syrian chemical attack that killed hundreds of civilians last week.

What’s sorely missing in the administration’s voluble discussion of the incident is a clear, compelling case to convince U.S. allies of the justification for an attack and a plan for what will happen after an attack, should Syria or its friends in Tehran or Moscow retaliate against the U.S. or its allies in the region. What if the damage to Syria’s war infrastructure isn’t sufficiently severe, and the Assad regime defiantly decides to double down?

The administration is scrambling for a policy on Syria. The result so far: a muddled mess. Obama, having long ago said that Assad must go and that Syria’s use of chemical weapons would cross a red line, has let his desires get ahead of his willingness — at least thus far — to enforce them. The clumsy timeline:

On Monday, U.S. Secretary of State John Kerry all but pinned the attack on Syrian President Bashar Assad.

On Tuesday, Americans awoke to news stories, clearly leaked by the White House, laying out fairly detailed threats on the duration and breadth of likely missile strikes against Syrian targets.

On Wednesday, President Obama said in an interview on PBS’ NewsHour, “We have concluded that the Syrian government in fact carried these (attacks) out.”

On Thursday, however, came news reports that U.S. officials have strong circumstantial evidence but no “smoking gun” proving that the order to attack came from Assad or his top commanders. Several U.S. officials said the intelligence linking Assad to the attack is “no slam dunk.”

What’s more, in that PBS interview the president telegraphed his likely military reaction, telling the world (Damascus, Tehran and Moscow included) that if he decides to attack, the Syrians could expect little more than “a shot across the bow, saying, ‘Stop doing this.’”

Why not keep the Syrians guessing about how big of an attack to expect and how long it might continue?

Obama is acting like he’s already decided to attack Syria and that he expects America’s allies to come along for the ride because, well, just because.

Given all this murky messaging, it’s not surprising that over the last couple of days, those key allies — and many members of both parties in the U.S. Congress — have told the president: Not so fast.

“This mass chemical massacre cannot go unanswered,” French President Francois Hollande said last week. Days later he said “everything must be done for a political solution.”

British Prime Minister David Cameron saw the House of Commons vote Thursday against British military action against Syria.

With customary allies flinching and Congress asking questions, what should Obama do?

Full stop. Now is the time for sharing the best intel available on the use of chemical weapons and for reminding other governments — and American citizens — that doing nothing, or next to nothing, would invite even greater atrocities. If there is to be an attack, it can’t be waged by a Coalition of One.