Star comment: Shifting sands of IS crisis
As MPs debate the prospect of Britain joining an international coalition bombing Islamic State, it is worth reflecting on the extraordinarily rapid shift in Western policy which has brought this nation to the brink of military action yet again.
It was only a little over a year ago that Prime Minister David Cameron was pushing for the arming of "moderate" rebels in Syria to try to overthrow President Assad's regime.
In January President Obama was airily dismissing Islamic State as junior league players. That was before the group conquered large swathes of Iraq and Baghdad itself seemed in danger of falling.
America was stirred to intervene when it became clear that tens of thousands of civilians were at risk from these genocidal jihadists.
That was a few weeks ago. Now those humanitarian grounds have been replaced by a general war against Islamic State, both in Iraq and Syria, to destroy the group or damage it so badly that the Iraqi military, and hence the Iraqi government, will retake control of those areas which have fallen under Islamic State's dark shadow.
Hardly anybody had heard of Islamic State in Britain. Then it became another far-off problem.
Now it is top of the agenda and, Mr Cameron contends, a threat to Britain's security.
We have become used to the televised fireworks display which is the overture to these interventions, as modern military hardware demonstrates its awesome capabilities.
It is in the messy aftermath that people start to look the other way, as in Libya, where following Nato's intervention Tripoli has fallen into the grip of Islamists, Benghazi is a place of fear and the government has fled to Tobruk.
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The descent of Libya into what the French defence minister has described as a terror hub has been an unintended consequence of an air campaign which was enthusiastically championed by Mr Cameron and supported by Parliament.
Islamic State is a group which glories in its own brutality. Its atrocities have outraged the world. Its televised beheadings have appalled and disgusted all right-thinking people.
Mr Cameron has a relatively "easy sell" in convincing MPs of the moral justification for joining the air campaign against the group in Iraq.
In embarking on this campaign, Mr Cameron must be clear on how he sees the path ahead. Because if Islamic State proves resilient, Britain will be in an open-ended commitment and there will be a chorus of voices calling for troops on the ground to achieve the objective.
See also: Shropshire MPs backing Camerons stance over air strikes on terrorists
