It would be unwise to attack Syria. But it would be more unwise to believe that a one-off slap will succeed.

President Obama now seeks Congressional support for an air-strike against the monstrous regime of Assad after it allegedly used poison gas against civilians. The purpose is twofold: it is punitive, to punish the regime for violating a long-standing international norm against the use of chemical weapons. And it is preventative, intended to disrupt the regime’s capability for doing it again.

In brief, this exercise in missile diplomacy strikes me as imprudent.

Firstly, the evidence is not in, not to a satisfactory standard at any rate. The same President that rose to prominence condemning the unilateralism and illegality of Bush’s war in Iraq is now pushing for a resolution in favour of bombing a country in defiance of the UN Security Council vetoes it would get, and weeks before the UN’s own deliberation about what happened is due. Personally I don’t regard UNSC agreements as morally compelling as some commentators seem to , given that it is made up of states that all carry out unilateral war when it suits them. But if war is to be waged – and that is what this is – surely the threshold should be sufficiently high for the evidence to be properly assessed. If it is so painfully clear that Damascus is the culpable party, then the evidence will reveal this. The bad faith and misrepresentation of evidence in building the case for Iraq haunts us still, and that is one reason the House of Commons has rejected Prime Minister Cameron’s plea for support for war against Syria. Now is no time to be cavalier about matters of proof.

Secondly, it places undue moral and political weight on one method of atrocity over others. Regimes kill civilians often and with much simpler methods that usually kill at a faster clip. Tyrants do not need poison gas to terrorise civilians, even if they think they do. A well-organised political machine, radio broadcasting and machetes killed people fast and on a great scale in Rwanda in 1994. As the wolfish assassin played by Tom Cruise in Collateral quipped, no-one has killed that many people that quickly since Hiroshima.

For some reason we attribute chemical weapons with exceptional barbarity, possibly because they are linked to the scientific genocide carried out by Nazi Germany in World War Two. But most slaughters, such as at Srebrenica, are done with cruder methods. And Assad’s assault on a neighborhood with poison gas seems to have been less murderous than his use of munitions, as hundreds of thousands of Syrians could attest if they were alive to tell it.

Either we say that chemical weapons use deserves more severe punishment than other methods, in which case an argument should be made as to why, precisely. Or we say that all outrages against civilians must be punished, which will put the weary, debt-laden, divided United States on a course Obama claims to oppose, a path of endless war.

Thirdly, Obama’s case for a limited bombing conducted to defend and consolidate a norm and prevent an aggressor carrying out one kind of atrocity places too great a faith in the effectiveness of a one-off act of war. Obama presents America as a judge dispensing justice to an offender in the dock, to teach it and everyone else a lesson, and prevent them doing it again.

But if America bombs Syria, it will not be handing down a verdict in a civilian court. Objectively, whether it likes it or not, it will be joining one side in a brutal and very messy civil war. The opposition knows it. The Syrian regime knows it. Onlooking states know it – Turkey, Russia, Iran -backing one side or the other. And Assad will likely conclude that the cruise missiles fired at him from the sea are not the instruments of international justice, but a declaration of war by a superpower joining the other side.

This will likely have consequences that Obama’s arguments have hardly addressed. The Tomahawk missiles will probably not topple Assad quickly, given the poor success rate of strategic bombing for regime change. They will, however, elicit open hostility and hostile retaliations from the regime and its backers. Assad will promise revenge, via cyber assaults on terrorist strikes against any American base, or American, he can get his hands on. Hezbollah and Iran will vow likewise and possibly also vow to punish Israel, America’s main ally in the region. And, distressingly, Russia’s hostility can be reliably expected across the board. America will find itself in an intensifying conflict where a coalition of enemies directly threaten it.

And herein is the problem: Obama wants a limited, punitive, one-off airstrike to make a point. But what he will get is something far more fraught: the opening shots in a new round of a war which will become more internationalised. Assad will likely survive and look defiant. This will make Americans, with little appetite for more war, feel humiliated, angry and/or frightened. For Obama, the downstream pressure to escalate will be strong.

And the slaughter of civilians will continue.

So, if America is to do this, let it not be a foolish slap conducted to avoid embarrassment. It should know that by stepping into this fight, it is joining a side, making fresh enemies and raising the stakes for itself. In which case, it must punch Assad with great force, not just slap him in a pinprick measure that is enough to kill bystanders and escalate the conflict, but not enough to succeed.

Given that public opinion and war weariness will circumscribe any military action to standoff strikes, they must be targeted at the regime’s capability to wage war across the board: its airpower, its cyber-capabilities, its command and control centres, its radar systems, its ships and its army on the ground. If America is determined to impress upon the world the extent of its presence and its power, and if it really does believe that this regime should be stopped in its tracks effectively, if it really does identify its security interests with the success of the Syrian rebels, then this is what is required.

If this sounds horrifically unacceptable, and if it sounds like the kind of thing Americans will not shoulder, then America’s policymakers should not delude themselves that a few cruise missiles will be a sensible substitute. Because stepping in to this war will very likely lead to mutual escalation. It is not just a matter of ‘knowing the enemy’, it is a matter of ‘knowing oneself.’ Knowing itself, Washington should realise that it itself will not tolerate the blowback from a bombing slap.

So, its go hard or go home.