What's the end game for air strikes against Islamic State?
The US-led air campaign against the so-called Islamic State (IS) is unlike many that we have seen over recent years. It is about as far away from "shock and awe" - the large-scale deployment of massive and overwhelming firepower - as you can get.
Its success is not to be measured simply by the tonnage of bombs dropped or by the number of air strikes on any given day. Air power is an important, but ultimately a supporting element in this campaign.
Its job is to hold the line in the absence of sufficient credible local military forces on the ground. Its first task was to blunt the momentum of IS and to begin the process of degrading the organisation.
Putting IS into reverse is for the medium to longer term and that will crucially only happen when local forces are trained, re-equipped and able to take the fight to IS on the ground.
The Syrian and Iraqi theatres are of course inextricably linked, even though some countries are reluctant to strike at targets in Syria.
For now there seems to be an effective division of labour, with the US hitting IS command and control targets in Syria; the US being joined by its Arab allies to hit at Islamic State's financial resources through strikes on oil refineries in the areas it controls.
And in Iraq the US has been joined in strikes by the French and the British. Now the Australians too have been given a parliamentary green light for combat missions.
By and large though the number of air strikes is limited. A typical update from US Central Command, for example that issued on 2 October, describes four strikes in Syria and seven against IS targets in Iraq.
This looks like what may become the general template, though clearly there will be spikes in activity, as there were during the initial US attacks on IS targets in Syria.
A surge in air operations can also be expected if IS forces begin to make significant new advances on the ground.
For now though it seems - at least as far as Iraq is concerned - to be a case of a weapons position hit here, an individual technical or armoured vehicle destroyed there. It doesn't necessarily add up to much. But something of an impact is already clear.
IS commanders are having to adapt to the new and more dangerous environment in which they are operating. So, fewer convoys of vehicles; greater effort to shroud communications; the air campaign making it that much harder for IS to marshal and concentrate its forces.
How far has the IS momentum been halted? It's fair to say that the picture is mixed, with static battle lines in some cases but reports of IS advances elsewhere.
So if the initial goal of the air operations is to try to relieve the pressure on Kurdish and Iraqi forces on the ground, it is still much too early to declare the mission a success.
In any case the majority of combat missions being flown are for gathering intelligence, and their number is dwarfed by those required to support the operations; tankers, command aircraft and so on.
In truth this is not a very efficient way to conduct an air campaign. Other than the US and allied aircraft operating out of Jordan, most of the bases from which these missions are being flown are very far from the target areas.
When Australian F/A-18 jets join the fray they will be flying from al-Minhad near Dubai involving some eight to 10 hours in the air with fuel needing to be replenished probably on both the outward and inbound legs of their missions.
That is why Turkey's decision to open its bases could be crucial, especially if a rapid surge in the tempo of the operation is needed.
That then, for now, is the air campaign. A pattern has been established and barring mishap or drama it will become common-place, receding from the headlines.
In many ways far more important will become the mission to bolster Iraqi and moderate-Syrian forces on the ground. This will take considerable time and may be a good deal easier in Iraq than Syria.
Training and the supply of equipment and ammunition for the Kurdish forces has already begun.
Re-establishing the credibility of the previously US-trained and equipped Iraqi army will take time. Important sections of the Iraqi military simply collapsed in the face of the IS onslaught.
But in a curious way, as the former US ambassador to Iraq Ryan Crocker has noted, the Iraqi military "was not rotten to the core. It was rotten at the top".
Effective commanders were replaced by political place-men by an increasingly sectarian government.
If Iraq's new prime minister can really establish a more inclusive pattern of governance then better commanders, replenished weaponry and some additional training could bring the Iraqi military back to a state where, with air support, it could embark upon significant offensive operations.
Syria though may be a very different case. Here the mantra from Western governments is about empowering the "moderate opposition" to counter IS, though it is accepted that selecting, vetting and then training even a few thousand personnel will probably take over a year.
These fighters - even if effective - will be battling on two fronts against both IS and the Assad regime. The complex patch-work of shifting allegiances in Syria makes this a very local civil war and it is hard to see how the Iraq model - if you want to call it that - can be applied there.
Battle of ideas
So this is a campaign where many of the biggest questions are still to be answered. The brutality and determination of IS is not in doubt. Its longevity may be open to question especially if local Sunni tribes react against its harsh rule.
But this is a battle of ideas as much as opposing forces.
IS as an organisation can be degraded from the air. It might be possible to defeat it on the ground, at least in Iraq. But destroying its ideology is quite another matter.
IS is after all simply an out-growth from an earlier branch of al-Qaeda in Iraq. That was defeated by an objective alliance of American troops and Sunni tribesmen.
That defeat produced the seeds of what became IS and the danger is that even if defeated, IS will simply morph into some other organisation.
This is perhaps what Western leaders mean when they talk about "a generational struggle".
And the chaos in Syria, for which there seems no resolution, provides an incubator for all of the complex strands that make up the jihadist phenomenon.