Time has come to think again about ways to stop Islamic State

Those in the corridors of power in Washington and the West too must be having a few sleepless nights over the relentless advance of the jihadists from the Islamic State (IS) group.

Barely days after capturing Ramadi the capital of Iraq's Anbar province, the terrorist army of IS seized full control of the historic city of Palmyra yesterday. This leaves countless civilians at its mercy and the world heritage site and its famed antiquities at risk of destruction.

If anyone has any doubts about the jihadi group's military capabilities then it is time to think again.

After their latest advance IS now holds sway over half of Syria's landmass, some 95,000 square miles according to the Syrian Observatory for Human Rights. This effectively pushes them ever closer to President Bashar al-Assad's strongholds of Homs and Damascus.

These gains come too despite sustained efforts lately by Washington to paint IS as a gravely weakened organisation.

Last week of course the US made much of a dramatic secretive raid into Syria by its special forces that killed high profile IS commander Abu Sayyaf, the mastermind who helped direct the group's oil, gas and financial operations.

But despite this single success events in Ramadi and Palmyra over the last few days have revealed the bankruptcy of claims that IS is a force on the back foot.

Far from suffering from resource and manpower shortages, the group is increasing its grip on the local populations in its strongholds of Mosul and Raqqa, Syria.

Worryingly too it appears to be sustaining its recruitment drive. To put this into some kind of context, the contingent of foreigners who have taken up arms on behalf of IS during the past three and a half years is more than twice as big as the French Foreign Legion.

This amounts to as many as 17,000 fighters from 90 countries according to one independent Western estimate.

In fact the conflict in Syria and Iraq has now drawn more volunteer fighters than past Islamist causes in Afghanistan and the former Yugoslavia, and an estimated eight out of 10 enlistees have joined IS.

According to the International Centre for the Study of Radicalisation, a think tank at King's College London, these now include around 3,300 Western Europeans and 100 or so Americans.

On a more immediate level though what does the loss of Ramadi and Palmyra, tell us about current strategy aimed at halting IS?

The first thing to realise is that the twin battlefield successes in Palmyra and Ramadi pile pressure on Damascus and Baghdad respectively.

Once again in the space of less than a year Iraqi soldiers abandoned their positions in considerable numbers in the face of advancing IS forces. This happened too despite renewed efforts by the US, Britain and others to train up and consolidate the battlefield ability of the Iraqi Army.

As a result, the scene now looks set for fresh tensions between Washington and Baghdad over the use of Shiite militias.

Washington is not keen on the deployment of the Hashd al-Shaabi, an umbrella organisation for Iranian-backed Shiite militias, but that is precisely what will now happen as Baghdad lets loose these militias in an effort to halt IS. Reports already suggest they are on their way en-masse as part of the campaign to retake Ramadi, raising fears of renewed Shia/Sunni sectarian strife in the country.

All too aware of such a possibility, the last time Baghdad countenanced such a deployment of these Shiite irregulars, Washington threatened to pull its air support cover. Should this again happen no doubt IS on the ground would be emboldened even further.

Which bring us to the thorny issue of the coalition air strikes themselves.

Tactically important and effective as they are, the latest IS gains suggest that relying exclusively on aerial bombardment will not be enough to stop the jihadists in their tracks.

Yesterday in Ramadi Iraqi forces said that they had thwarted a third attempt by IS fighters to break through their defensive lines east of the city. Exchanges of

mortar and sniper fire were reported across the new frontline in Husaiba al-Sharqiya, about halfway between Ramadi and a base where an Iraqi counter-offensive to retake the city is being prepared.

In Palmyra meanwhile the news was equally bleak with the world looking on horrified at the prospect of yet more mass killings of civilians by IS and the deliberate destruction of this archaeological and cultural landmark site.

From a strategic perspective also the fall of Palmyra is significant given that it is home to modern army installations and situated on a desert highway linking government-held Damascus and Homs with Syria's mainly rebel-held east.

And so the IS juggernaut rolls on leaving in its wake the most horrific atrocities and destruction.

As to how it can be stopped some serious rethinking will have to be done from Washington to Baghdad and beyond.

Could it be that the time is fast approaching when the West and its coalition allies will have to take a more assertive approach on the ground with all the profound implications that would bring with it?

How else one wonders can the abomination that is IS be halted in its march across the region and before it breaks down the gates of the citadel itself?