War, then. Another war. Still another war begun because the last guaranteed-conclusive war produced consequences that made one more shot in the dark inevitable. Intellectual and strategic failure is on a production line.

One new principle, if principle is the word, has been manufactured in a nod to the grisly cycle. When satire is outstripped by reality, it almost counts as funny. Those who treat air power as a single-use implement, David Cameron chief among them, have become practised in the art of uncertainty.

The Prime Minister grants at every turn that nothing is sure in this life, that of course he cannot promise increased domestic security, that obviously he cannot say how long the campaign will last, that clearly Islamic State (IS) might be eradicated soon. But still we have to do “something”. That’s the plan. Churchillian it is not.

Mr Cameron strains for the appearance of honesty. He takes pains to answer questions. He does not quibble over the right to dissent. Today, MPs will have 10 hours in which to interrogate his “case for war”. If Tony Blair is watching from some penthouse suite, he ought to feel more than usually ashamed.

But the Prime Minister too is dishonest, in his emollient way. Were a majority of MPs not habituated to the lazy habit of airstrikes, they would throw his case back in his face like so much scrawled homework. As the truculent Tory, David Davis, has been pointing out, Mr Cameron has no end in sight for his new war. What kind of strategy is that?

When does the Prime Minister intend to admit to the public that “the long haul” could be far longer than they have dared imagine? Assassinating a few psychopaths with missiles and Raptor drones – if even that is believable – will not be the end of it. When the RAF delivers the first footage of a truck flaring into oblivion, that will not count even as the end of the beginning. Voters are entitled to be told what the Pentagon already knows.

They have a right, too, to hear Mr Cameron proving the part of his case that involves those “70,000 anti-IS ground troops”, the ones without whom his war cannot be won. No one else believes such a force exists. No one – not even the MPs ready to give the Government its war – believes that such a force will be created. So what follows when that army fails to materialise from the desert mists?

For or against, some MP had better ask the question today. Is Mr Cameron prepared to promise that British ground troops in battle order will never be committed? If not, why not? He might one day be able to make still another case, enlist the usual media suspects, and persuade voters. For now, the people he is supposed to be protecting have a right to know where this is leading. If airstrikes fail, what follows?

Ten hours of questions should pass easily enough. When does Her Majesty’s Government begin to tell our Nato partner, the Republic of Turkey, that attacks on the Kurdish Peshmerga are unacceptable? The Kurds possess the only one of those scattered regional forces with any record of success against IS. If the Turks won’t pack it in, and won’t cease their involvement in the IS oil trade, what is the Nato alliance all about?

Oil – of which the Prime Minister has said almost nothing – would also be worth an MP’s question. In order to sustain its fantasies of statehood, therefore of “caliphate”, IS needs the trappings and revenues of a 21st century entity even before it meets the costs of warfare. Will the RAF be putting IS-controlled oil fields out of action, Mr Cameron? If not, why not?

Emollient as ever, the Prime Minister would no doubt concede that it’s all “complicated”. Since confronting Saudi Arabia forms no part of his “case”, that issue must be complicated indeed. It does not alter the fact that “individuals” in Saudi and elsewhere in the Gulf have been crucial to the funding and arming of IS. Yet the UK, grateful for those trade and munitions deals, would prefer to bomb rather than annoy royal tyrants?

Tyranny is terribly complicated. Beyond uttering “£1 billion” as a catch-all answer to every question about his war’s aftermath in Syria, Mr Cameron has said little. Is the overthrow of Bashar al-Assad still a declared British aim? Or has the ambition been abandoned now that Russia’s Vladimir Putin is an almost-ally in the effort to eradicate IS (while Russian jets bombard some of those “moderates” earmarked for the 70,000-strong ground force)? Complicated, eh?

It could not be otherwise. The problem that will return to haunt Mr Cameron is his failure to spell out how hellishly complicated “doing something” might become. To a point, this is irony of the blackest sort because the Prime Minister is right about one thing. IS are not inviting our consent to their war. With no response, those who deal in slaves and decapitation to make a point about faith will not leave us alone. But which response?

Mr Cameron is vague, deliberately so. Today he will win a Commons vote for a bombing programme that even its supporters struggle to explain. That’s dangerous for Westminster democracy and lethal for innocent strangers. If the gesture of airstrikes fails, as it will, things will become enduringly bloody. A Prime Minister should be made to speak to the question: what will he do in that event?

He could bomb the oil fields; interdict financial systems; and at least call a conference on the global arms trade. Then he could wait – it would only take a second – for every vested interest to explain how complicated things are. Alternatively, he could explain to the peoples of these islands why he has no such plans. Too many of them have been led to believe that blowing a few bearded murderers to smithereens will sort things out.

The absence of a functioning official Opposition is hardly an asset. Jeremy Corbyn is the prisoner of his shadow Cabinet now. They have fettered him. They can do it again in future, and at will, until activists rebel and fabricated rows over deselection and “bullying” begin. Then the fraction of the public that still cares will wonder if Labour’s policy on blood sports has been revised.

Like the party, it’s mostly irrelevant. The important point is this: when Mr Cameron’s war leaves us with a hellish mess, what will the Labour MPs who vote for it today have left to say? And how will Mr Corbyn respond? With a free vote?

The Scottish National Party have no such problems. Fans of airstrikes – speaking with one voice, oddly enough – find SNP unity sinister. There, however, is another complication: Nationalists and a few others are the only ones left able to hold the government to account if a debacle commences. In a British institution, it can never be enough.