The reason that U.S. President Barack Obama passed the buck on authorizing a military strike on Syria to Congress is not because getting congressional approval is the constitutional thing to do. It always has been, although presidents have regularly denied it. Rather, Obama passed the buck to Congress because it was the only way out of the dilemma that he imposed on himself when he declared the use of chemical weapons to be a red line, without having thought through whether or how to go to war if the line was crossed.

When the red line was crossed, the administration’s belated search for military options faced two contradictions. The first was between the strong incentives to retaliate against the government of Bashar al-Assad and the wide opposition in both the United States and outside world to U.S. military action. The second was between the amount of force that would have a chance of producing useful strategic results and the amount that is politically tolerable. Even among those who demand action, pressure to use U.S. military power is exceeded by pressure not to use very much of it, for fear of entanglement that clearly does mean war.

A responsible choice for Congress and the president must at least be one that does not make things worse. All things considered, that could mean backing away from the threat of action so clearly implied by Obama weeks ago, even though that would be an embarrassing retreat. By accepting the embarrassment, those members of Congress who vote against authorizing the use of force can resolve the two contradictions. But those members who choose to back the president must also, in effect, endorse the intent to use modest amounts of force. That endorsement should, in principle, rest on a sober comparison of what all the potential strategies, including those already rejected out of hand, can be expected to accomplish at an acceptable price. What any strategy can do depends on the fit between political objectives and military operations designed to achieve them.

Logically, there are at least six potential objectives, some of which overlap. These include a symbolic statement against war crimes; punishment of the Assad regime for its crimes; coercion of the regime to change its policy; ending the war, eventually, by helping to defeat Assad; demonstrating credibility to foreign audiences; and demonstrating credibility to domestic audiences. And assuming that the United States has no intention of marching into Damascus, the operation’s half of the equation rests on precisely how limited the air strikes will be. “Limited” air action can range from a few symbolic strikes with minor material impact to a seriously destructive campaign against dozens of targets over the course of several weeks.

Obama made clear before passing the ball to Congress that attacks near the mild end of the spectrum would be the only ones he would countenance. In truth, American air strikes on any scale may not serve some of these objectives. But the most limited attacks are likely to be the least effective for any of the six objectives except the first and the last -- which are the least strategically valid ones. Indeed, the lightest strikes could prove not just ineffective for the most important purposes but counterproductive.

Symbolic use of force can be accomplished with very small-scale strikes. They register stern disapproval of the enemy’s atrocities, and may also serve the last of the six objectives, pre-empting domestic critics waiting to berate the Obama administration for complete fecklessness. Strategically, however, they achieve nothing positive in a brutal war where the contestants are used to paying high costs every day. Pinprick strikes actually signal a lack of serious purpose, and weathering them is a badge of honor for a weak regime confronting a superpower.

Punishment, pure and simple, is the most obvious rationale for retaliation. Assad can be made to pay a price for crossing Obama’s red line, even if the retaliation accomplishes nothing more. There is something to be said for making the point that, even if governments can survive after committing war crimes despite U.S. warnings, they cannot do it for free. That may help to deter third parties in future conflicts. But to make punishment impressive means inflicting damage that is severe. Even if the operation is stronger than pinprick action, destruction from American bombs will appear ineffective if the regime can absorb it as easily as the damage that has accumulated from day to day throughout the war. The more dramatic the price that the United States exacts in the form of damage, the better its strategic point is made.

Coercion -- to deter Assad from further use of chemicals, or to compel him to make political concessions -- would apply punishment toward a more ambitious and difficult goal. Some theorists have argued that restrained use of force can be effective at signaling to a targeted government that it stands to lose much more from subsequent escalation if it does not concede. That idea makes some logical sense, but it has not been borne out in many actual wartime cases, if any, as research by Robert Pape, professor of politics at the University of Chicago, and others has shown. In any case, this strategy depends on intent to up the ante with stronger force if restrained attacks don’t get the desired result.

The closest thing to an example of successful coercion by air attack alone was the war over Kosovo, but that was a massive 78-day assault (surely the outer limits of the concept of “limited”), and it inflicted a huge amount of destruction on Serbia and its civilian population. It proved vastly more costly to NATO than world leaders anticipated at the outset -- they planned no more than a few days of bombing. Finally, there is yet much uncertainty over whether Serbia’s surrender was due to the air war or to other causes, such as the prospect of invasion on the ground or withdrawal of Russian diplomatic support. In any case, the Obama administration has made clear that it does not intend to bomb on the scale of the Kosovo war.

Historical evidence suggests that trying to coerce the Assad regime to make concessions to the rebels would be a long shot, and that, for it to have any chance, it would require a bombing campaign more intense and prolonged than contemplated. And what if only the more modest purpose is declared -- to deter Assad from further use of chemical weapons -- but the regime nevertheless does it again? That would box the president into a choice between embarrassing failure and open-ended escalation, and it would raise messy questions about what an initial congressional authorization meant for that new choice, which would place Obama and Congress in a more terrible bind than they faced at the outset.

Ending the war -- by adding enough U.S. power to the equation to enable rebels to eventually defeat Assad -- is the most ambitious possible objective. It could also be the most legitimate, since, rather than the indecisive and ambiguous psychological effects from a modest attack, it would offer a clear material benefit to justify American action that kills people -- which, make no mistake, is what the use of military force is about. Although it may be the most legitimate objective for an act of war, however, it is the least plausible for Syria. First, there is no constituency in the United States anywhere on the political spectrum for action that is seen clearly as going to war, and there has been no apparent consideration within he administration of an option for limited action that is intense, prolonged, and decisive. Second, even a massive air assault would not be guaranteed to defeat Assad. Third, and most problematic for all of American options toward Syria, there is no reason to believe that a military campaign that worked would produce a good result -- that it would be good pro-Western rebels who take power, rather than bad Islamist radicals even worse than Assad. Thus, the administration has already made clear that the aim of American force in this case is not regime change. But then one might ask the proponents of air strikes: If not to help end the war by either coercion or outright victory, are the other objectives a good enough warrant for using indecisive force that kills people?

Foreign credibility as a concern assumes that other governments will not take American deterrent threats seriously if they see Washington back down from one. This concern overlaps with the rationale for punishment as an objective. Research on previous cases by Daryl Press, a professor at Dartmouth, however, has shown that concerns about credibility are overblown. Nevertheless, it will not be a good lesson for reckless regimes if Obama fails to follow through on a deterrent threat. Since Iran and especially North Korea are more potentially dangerous than Syria, this is not a minor concern. Affirming credibility in the eyes of hardened dictators, however, most probably follows from success in achieving some significant strategic objective. Punitive attacks that appear paltry, indecisive, and bearable will not convince third parties that you can’t get away with crossing Uncle Sam at an acceptable price.

Domestic credibility is a dubious justification for bombing another country, but it inevitably looms large for politicians in a democracy. Despite fervent demands from some, like Senator John McCain, however, Obama’s bow to Congress reflects the strength of opposition to combat action. Obama is damned if he does and damned if he doesn’t. As is usual in politics, compromise between conflicting demands may seem the path of least resistance. Light and brief air strikes are attractive because they do something to undercut hawkish critics, and they alarm dovish critics less than stronger action. But practical political compromise does not always make sensible strategy. As the greatest philosopher of war Carl von Clausewitz wrote, “A short jump is certainly easier than a long one: but no one wanting to get across a wide ditch would begin by jumping half-way.”

As with other post–Cold War atrocities, the use of chemical weapons has led to calls for the United States to “do something” to stop the perpetrators. Yet exactly what that something should be -- which would not make things worse, not cost too much in blood and treasure, and not have unanticipated consequences -- is utterly unclear. The two contradictions make the policy problem a dilemma in the true sense, a choice among unsatisfactory options. Congress must now share responsibility for determining the least bad way out. Indecisive use of military power emerges as the compromise between apparently unacceptable alternatives of doing nothing and doing too much. This is jumping halfway across Clausewitz’s ditch; it is solving Solomon’s choice by actually splitting the baby. In other words, it is politically logical but strategically unwise, and it is both understandable and tragic.