All wars have a turning point.

All too often that pivotal moment is never visible until well after it happens.

Four years into the Syrian conflict that has claimed the lives of more than a quarter of a million people and caused the suffering of many millions more have we finally reached that turning point?

Has that critical moment arrived when the direction of the war in Syria is shifting irrevocably and simultaneously against both the regime of President Bashar al-Assad and those Islamic State (IS) fighters seeking to oust him?

It would be a brave if not foolish analyst that would say unequivocally that was indeed the case right now. I for one would urge caution over such an evaluation. That said there are undoubtedly signs that the battlefield tide may be turning.

This assessment I should stress has nothing to do with Defence Secretary Michael Fallon's paving of the way yesterday for Britain to join US- led airstrikes against IS targets inside Syria.

Instead it is predicated on what might be called the internal dynamics of the war the logistical and military condition of its protagonists and pressure being brought to bear by regional players.

Let's begin with the situation as seen from the perspective of the Assad regime. In a nutshell it now finds itself in an increasingly vulnerable position.

Almost daily the headlines on the website of the official state Syrian Arab News Agency (SANA) do their best to remain upbeat and suggest all is business as usual.

"Army foils terrorist attack in Daraa", announced one headline rather glibly a few weeks ago, while another recently told how the "Homs Clock ticks again, declaring the return of life to the Old City".

The reality of course is somewhat different with growing evidence that

Syrian government forces are finding it increasingly difficult to hold ground. That much was clear as recently as March when rebel forces retook the town of Idlib, helped in great part by arms supplied by Turkey and Saudi Arabia who for once worked together instead of backing rival rebel groups.

Other cracks are showing too with the Syrian currency plummeting in value and schisms appearing among the higher echelons of the security establishment.

So bad have things been on the frontline that even SANA had to step back from its spin when last month Assad himself acknowledged military "setbacks" in a public address.

Faced with such challenges at home the beleaguered Assad cannot even look confidently to his traditional allies overseas for succour and support as he once did. There has been much speculation lately that Moscow is shifting its stance on its old ally in Damascus. Military economic and logistical support is said by some sources to have been reduced as Russia ways up a future without Assad.

Other options may be on the table. At the G7 meeting earlier this month, British officials were said to be floating the idea of a diplomatic solution and the talk of Russia offering Assad asylum refuses to go away.

Perhaps Moscow is finally realising the flaws in the notion that the Assad regime is the last bulwark against IS.

And speaking of IS and its jihadist fighters, I mentioned earlier that the tide of battle might be simultaneously turning against them as much as it is against the Assad regime. Both parties being on the back foot would of course be music to the ears of Washington and its western allies looking to a future Syria without either Assad or IS calling the shots. But we are a long way off yet from that.

The terrible irony is that the killing of civilians in IS-inspired terrorist strikes from Tunisia to France has focussed the minds of the international community on dealing with the war in Syria in a way that the deaths of quarter of a million Syrians seemingly could not do.

In short IS's own transnational terrorist ambitions may be the very factor that will force a change of strategy on Syria. For four years now the international community has vacillated in its response to the carnage in there and one senses a ground swell of political will to do more to neuter the IS threat. The tricky question of course is just how Syria and its long suffering people will benefit from this along the way.

Regional players too are making their own presence felt on the conflict like never before.

Turkey who fears resurgent Kurdish separatists inside its own country is said to be considering sending troops across Syria's northern border to establish a buffer zone. Jordan is considering doing likewise. As Channel 4's international editor and long time Middle East watcher Lindsey Hilsum rightly highlighted recently, Jordan too has been hosting American troops who are training a moderate force rebel force, ready to fight both Assad and IS.

This certainly is what Washington, UK and other western allies want more than anything, a group that can take the fight to both IS and Assad and are politically malleable and easy to rein in.

This of course is the Middle East where things rarely go to plan and monster regimes are just as easily created out of efforts to get rid of existing ones.

Yesterday it was business as usual with regards to US-led coalition airstrikes against IS. Eighteen sorties were flown in Iraq and 10 in Syria.

Whether we can expect to see more in the coming weeks that include British aircraft participating in the Syria operation will depend on whether MP's back the launching of strikes - even if this is not a prerequisite for any government decision to go ahead.

As I cautioned at the beginning of this analysis it would be unwise to suggest that the Syrian war has reached any definitive turning point. That it's entering a crucial phase however is I think without doubt.