We will go in militarily, if not with "boots on the ground" if the mission purpose has clear humanitarian goals, and if the risk to our people is acceptable. We don't want an enemy near enough to slit Australian throats.

"Should we be asked, we would want to look at any request in the light of achievable objectives, a clear role for Australian forces, a full risk assessment and an overall humanitarian objective," he told parliament on Thursday, in what may well prove to be the only sense in which parliament is involved in the process.

It is by no means clear just who is, or will be, doing the risk assessment. Most of the risks, local or international, are political ones, ultimately for politicians, not generals or air vice marshals to make. Military folk tend to follow the mood and the instincts of political leaders, whether they agree with them or not. There are few deep reservoirs of military wisdom around in Australia, hardly surprising given that it must be 74 years since a single thing done by Australians in action had the slightest effect on world-wide events.

Our generals and military advisers will be discussing what can be done and with what, and with what prospects of casualties, not whether the cause is just, the means proportionate, predicting the responses of players and calculating the chances of success. It is by no means clear, in any event, just what sort of success we want or can hope for.

Is it to achieve a simple intervention designed merely to stop the slaughter, perhaps by interposing ourselves between those with the knives and those with the throats?

Is it an intervention designed to wipe-out the mini-army of the Islamic State, so powerful that several thousand at a time can make Iraqi armies of 50 times bigger run without firing a shot? Can that be done by raining hell from the air, but without boots on the ground? Could it be done even by boots on the ground, particularly foreign boots?

Is it to stop a Sunni Islamic State? Is it to protect the territorial "integrity" of Iraq and Syria, each of them, like Lebanon, Jordan and Palestine created by a secret agreement made by the French and the British about 100 years ago? Is it to prevent the creation of a new Kurdistan? Or to confirm it as a belatedly realised good thing and area of refuge?

Where do we stand on side issues such as the control of Syria, the good governance of Iraq, and the keen interests of states such as Turkey, Jordan, Iran, Saudi Arabia and Israel in the nature of the outcomes?

Perish the unworthy thought that any of our enthusiasm for joining in this, the Third, Fourth or Fifth Crusade against the Infidel, owes anything much to the anger and indignation of the Administration of the United States about the cutting of one of its journalist's throats. Or that we can big note ourselves as a dependable and willing ally, without actually having to do very much.

Our allies are, like us, somewhat gunshy about "boots on the ground." The chance that any operation can actually improve the lives or the deaths of those we will have come to save is minuscule. It has, for example, yet to be established, after 100 years of aerial warfare that bombing from the air has ever made a material difference to the outcome of any conflict. The results of strategic or tactical air warfare are, generally, the more dubious in situations such as the one we may be going into, where there is already significant asymmetry between us and them. Ask Israel, which just lost its recent war against Gaza, simply by not winning. Ask the Americans of Hanoi, or the Americans of the First and Second Crusade against Iraq. Ask NATO about the efficacy of strategic or tactical air war against the Taliban. Or, for that matter, the Russians against much the same chaps, 30 years earlier. Landing a million dollar missile on a $20 tent may be clever, but rarely changes much.

Some of our allies have agendas that are not, or should not, be ours. Saudi Arabians have been bankrolling the Sunni mischief in Iraq and Syria, even if some are now somewhat alarmed at how vicious their terrorists are, and now want them to be nicer, particularly about Saudi leaders. Iran is hostile to Saudi Arabia and has much influence over the Shia of Iraq, and, separately, Syria. Quite separately, it and Turkey have traditionally been hostile to any idea of a Kurdish state.

Again there's the question of whether we still want regime change in Syria, preferring President Assad and such "stability" as his regime can offer, to the chaos and disruption of a disintegration of Syria and Iraq, or a militant, murderous and expansionist Sunni on the borders of Turkey. There's Turkey, notionally not only our ally but generally a force for secular reason in the neighbourhood. It has been playing various Machievellian games with the Sunni insurgents (who are co-religionists) and who hover between providing refugee camps for more than a million displaced people, victims of the fighting, and providing refuge and supply lines to those creating the misery.

Mention of Turkey may serve as a reminder that Turkey is not only involved in uncertain domestic politics, but an active and an interested player in events on the other side of the Black Sea, involving the Ukraine, Russia, separatist movement by ethnic Russians, and Georgia. For a nation such as Turkey, many of these problems converge in a way that may serve as a reminder that Russia has interests in the fate of Iran, and a balkanised Mesopotamia. There's Israel, and the Israel-Iran confrontation, mostly through proxies such as Hezbolla and Hamas.

In the recent history of the Middle East, say the past 200 years, parties, factions and groups on the ground have generally outthought and outstrategised all outsiders, mostly playing us, rather than being played by us. There is not the slightest reason to think this is different with the latest possible adventure.

Our intelligence has never, in the past, had any insight into what the "enemy" is thinking, or doing, or about what will happen if, or once, the Westerners re-enter the arena.

Slitting throats is on the side of barbarism, (up there, indeed, with using napalm, poison gas, cluster bombs and land mines, all things Westerners have done in the past) but it is effective, perhaps even ethically justifiable as a deterrent that actually saves lives. It is a particularly cheap way of doing ethnic cleansing.

This does not justify or minimise its evil. But we are ourselves morally careless when considering the incidental effect of a bombing campaign (in, say Gaza), or an expedition against civilian enemies, such as Fallujah.

Ruthlessness, barbarity and unpredictableness helps deter reconnaissance, and small unit activity. Having the enemy terrified works well in war.

Many observers think that internet throat-cutting is done to lure the west into yet another intervention it cannot win. By this theory, cold-blooded men are pressing our buttons and they, not we, are in control of events. We must have enormous faith in our capacity to outsmart them. History has not proved that such evil geniuses can be eradicated by drone strikes, strafing or counter-terror from five miles up. We must also know how intervention can be simultaneously in their interest and ours. WE must show how our national interest is engaged.

Is the bit part being planned for Australia primarily to show that we are a reliable ally of the US? Do we have any confidence that the political and military genius of the US has thought through, and considered the risks, developed tactics and strategies for dealing with them, and can outthink and counter the enemy's responses? If so, whence came this sudden wisdom, given that it has not been evident in any recent interventions, whether from the White House, the Pentagon or commanders in the field?

We now mostly admit that we "failed" in Iraq mark I and II, and in Afghanistan mark I and II, as well as Syria, the Ukraine and Georgia, and that "we" must not repeat such mistakes. We must have cool-headed and realistic goals, and, probably, must be more realistic about the baseness, venality and perfidy of the allies we think we are there to protect.

In our past failures we did much more harm, short and long term, than good to the civilian populations involved. Indeed we converted many neutral civilians into passionate and deadly opponents. Our intentions, apparently, were good. But meaning well is not enough. And our intelligence and judgment proved to be badly awry --in part because we listened to people who had good reasons to lie. Many of the same people are lying to us now. There are players, people who are supposedly on our side, who are in every respect as bad as players on the other side, and for whose interests, and on whose word, not a single Australian should be put at risk.

My own guess is that there is nothing outside intervention can do that can prevent a considerable redrawing of the maps of the Middle East. New borders will reflect the limits of majority settlements (and military victories) of the various religious, ethnic, and tribal locals. Just what room these new mini-nations will have for minorities, such as Azidi, Christians and Jews, is not clear. Likewise with peace between Islamic sects, or Israel. The tolerance of the new national leaders will be determined rather more by the diplomacy and statesmanship of the rest of the world, rather than the coercion of its bullets or bombs.

External force has hardly ever had much long-term impact in the Middle East. Australians, for example, have captured Damascus twice in the past 100 years, without a slightest evidence remaining of our being there. Each time foreign invaders, or peacemakers, or humanitarians have arrived, they have achieved little. If they have come with force - they usually do - those with, on paper, the most do not prosper long. If the use of force has been disproportionate, it has been the victim, not the perpetrator, who has ended up with the moral edge.

That's been the fate of the US, and before it France, Britain and the Ottoman Empire. It is the reason why support for Israel is now foundering. It will be probably the reason why the IS radicals will perish in the sand too, if not before they despatch yet another ill-considered western invasion.