There’s something morally perplexing about President Obama’s stance on the war in Syria. It’s not any clearer in its strategic logic.

The president watched—that is essentially what he has done, all the verbiage aside—while Bashar al-Assad’s army and the paramilitary shabiha, most recently joined by Hezbollah fighters, have some slaughtered some 93,000 Syrians. Now he has changed his “calculus” and decided to arm the Syrian insurgents, albeit in a limited fashion, because he has become convinced that Assad has used chemical weapons in his fight to the finish, killing about 100-150 people.

Obama declared last summer that Assad’s use of such weapons would be a “red line.” What he didn’t explain (and hasn’t still) is why that is worse than leveling of entire urban neighborhoods and killing of tens of thousands of innocents. Both are evil acts to be sure. But is the second on a different moral plane altogether, especially given that using chemical munitions (sarin seems to be the Syrian regime’s compound of choice) has not been to integral Assad’s battlefield strategy? Maybe so. But the president, despite his silver tongue, has surely not explained why it is.

The shift in Obama’s policy is more than a moral curiosity. It has set the stage for America’s direct involvement in a horrific civil war—but without any explanation from the commander-in-chief of what his guiding goal is. It’s not to prevent Syria’s chemical weapons from getting into the hands of hostile third parties; the president has not said that has happened or that Assad can no longer maintain control of these weapons. What then accounts for the administration’s tortured decision to arm the rebels?

One explanation that the White House has offered is that Assad’s use of chemical weapons necessitates a change in policy. But U.S. intelligence agencies have been careful about stating how confident they are about whether chemical weapons were used for sure, and if so in what quantities, how often, and at what cost in human lives. More recently, their confidence seems to have risen, but Syria is now a murky battlefield with multiple participants, and it’s getting even murkier. The president can’t be expected to divulge the sources U.S. intelligence agencies have relied on to find out if Assad has used chemical weapons, but he can surely provide a fuller explanation than he has so far.

There are two reasons why he should do so; the first has to do with the past, the second the future.

An Exemplar of Confusion

Not long ago confident, public assertions by American officials that another brutal regime had weapons of mass destruction paved the path for a war that lasted nearly a decade. It cost more than $800,000,000, led to the deaths of nearly 4,500 American soldiers (and many more Iraqis), wounded about eight times as many, and left behind a country so torn by sectarian war that its cohesion remains in question. The point is not that we’re headed for another Iraq; that’s hardly likely. It’s that in the recent past, confidently proclaimed intelligence findings that proved stunningly inaccurate had major consequences. That alone warrants caution about what is now being offered as the basis for what, the president’s desire to calibrate his involvement notwithstanding, will amount to a big change in U.S. policy in Syria.

It is of course quite possible that Assad has used chemical weapons—he is not a squeamish man—but it’s also true that there are many parties, inside and outside Syria, who want the United States more deeply involved in its war. They doubtless took note of Obama’s “red line” warning, realizing that his categorical commitment would effectively box him in were evidence found that the Syrian government had used chemical agents.

As for the future, there are two questions for the United States in light of President Obama’s decision to arm the anti-Assad forces: “What now?” and “How does this end?” Alas, on neither one has the president been clear. Worse, his administration is an exemplar of confusion. Obama’s decision is not a sound policy change; it’s a reluctant president’s effort to deliver on a commitment and to appease war hawks but without doing any more than the minimum. His deputy national-security adviser has said that the president does not plan to send “major weapons systems” to the insurgents or to establish a no-flight zone over Syria. The president’s mistake is to assume he won’t have to do more than what he wants to do and that he can resist advocates of deeper intervention at home and events within Syria. He is now hostage to both.

The president’s decision, it appears, is to supply the resistance with small arms and ammunition. But the reason given for doing this is not that it is meant to punish Assad for using chemical weapons, though that, according to the administration, was indeed the catalyst for Obama’s announcement. Instead, it’s to change the balance on the battlefield and to reverse the gains Assad has made, especially since the fall of Qusayr this month and the added momentum his forces have gained since that success.

But how will small arms and ammo have the desired effect when Iran and Russia have been delivering Assad armaments that are much more lethal, and in large quantities? One is left to conclude either that Obama’s decision amounts to a symbolic move, or that it is a prelude to larger arms deliveries by the United States, something that would require the presence of American intelligence operatives and trainers on the ground. It’s not hard to understand why the president wouldn’t want say that the latter is in fact the case: Americans are not in favor of intervening in this war.

Besides, it will take time for the battlefield arithmetic to be changed even if there are major arms deliveries to the Syrian opposition. Meanwhile, Assad will surely scale up his offensive, which would of course also ratchet up the killing. But would that force Obama to order military strikes against Syrian military units and command and control posts so as to restrain Assad? If not, how long will it take before the resistance can be more effective against the regime, and what of the increased tempo of killing that would occur in the interim? Would the president find it morally acceptable and politically possible to wait while the resistance stages a comeback?

More likely, Obama would come under pressure by hawks—within his administration, in the Congress, in think tanks and in the media—to stay Assad’s hand by ramping up America’s military role. If he heeds the advice of the interventionists and orders airstrikes, it stands to reason that he would have to destroy Assad’s air defenses and to then institute a no-flight zone that prevents Assad from hitting insurgent redoubts and moving his forces around. Assad has better equipment than Muammar el-Qaddafi did and may well resist, and that raises the possibility of U.S. aircraft being shot down or pilots ejecting and being taken hostage. If that happens, the United States would presumably use tougher measures so that Assad surrenders soon.

Then there’s the external dimension. Once the Iranians know that American munitions are actually about to start flowing to the resistance, they will likely accelerate their own deliveries, calculating that they have short span of time to do so because it will be tougher to get supplies through later. Will the president destroy the airfields that Iranian planes have been using so that Tehran cannot increase arms shipments to Assad? And what if Russia decides to continue supplying arms to Assad and actually delivers the S-300 air-defense system it claims that it is bound by contract to provide Syria? Then there’s the flow of Hezbollah fighters and Shia paramilitaries from Iraq. What steps are envisaged to stop it? And what of Lebanon, which would almost certainly come under even greater strain as Sunni-Shia violence, already on the rise after Hezbollah’s entry into Syria, gets worse? How do we keep Lebanon from descending, once again, into the hell of civil war? What happens if that occurs anyway?

The “how does this end?” part is no less difficult. The administration says that the balance on the battlefield has to be changed if the resistance is to enter peace talks holding any kind of credible hand. Fair enough. But that’s not going to happen soon unless the United States delivers more than small arms and bullets—and does so rapidly and in large quantities. And even if Assad’s position deteriorates as a result, he would presumably wait to regain lost ground before going to the bargaining table. The upshot is that the administration’s stated rationale for its change in policy precludes any quick end to the Syrian horror show.

The best forces fighting Assad are the radical Islamists, organized in such groups as Jabhat al-Nusra and Harakat Ahrar al-Sham. The Saudis and Qataris would be pleased to see them take power in Syria. They are backing them partly because Syria’s civil war is also a conflict between the Sunni Gulf monarchies and Shia Iran; each has Syrian proxies. But the United States should have no use for these groups and others of their ilk. Indeed, among the reasons the Obama administration wants to supply the resistance is to change the balance of forces within the opposition between the hard line Islamists and other groups, who are said to be secular, moderate, democratic and other good things besides. But sending arms into the complicated, confusing Syrian battlefield requires (or certainly should) that there be a high degree of confidence that the weapons will only get into the hands of those deemed to be good guys, and will stay there. The mechanisms by which this can be ensured are unclear.