Is a Turkey-Saudi Arabian alliance the key to ending Syria's bloody civil war?

Much of the talk about Turkey during the Syrian civil war has rightly or wrongly been as an enabler. It has been across the Turkish borders that foreign fighters have slipped to swell the ranks of Islamic State (Isis), and across those same borders that looted antiquities have been sold to boost Isis coffers.

Turkey was among the first Middle East nation to back to the uprising against Bashar al-Assad, providing refuge for fighters and leaders of the Free Syrian Army (FSA) despite its proximity and long porous border with Syria that opens the country up to significant reprisals should Assad triumph against the various forces that are pitted against him.

This early support grew increasingly complicated as the FSA waned and was replaced with Sunni extremist groups such as Jabat al-Nusra and Isis. Turkey is against Assad, the Islamist militants are against Assad: the enemy of Ankara's enemy is its friend. Better a radical Islamist alliance than a powerful regime headed by a man it had publicly shunned and opposed.

"Turkey has played a dangerous game and come up short. They made a call early on that [Assad] would go quickly," said Julien Barnes-Dacey, a senior policy fellow European Council on Foreign Relations (ECFR).

On the other side of the Middle East, at the bottom of the Arabian Peninsula, lies another geo-political mess. Saudi Arabia's war in Yemen is not going as planned. The Houthi rebels it opposes are hitting back, scoring significant wins in the southern city of Aden and attacking Saudi border points in the north. The coalition it assembled looks reluctant to commit ground troops (Pakistan has pulled out and Egypt looks poised to) and the Houthis are emboldened.

When the grand Sunni coalition was first assembled with the intention of unseating the Houthis from Sana'a and re-installing deposed president Abdrabbuh Mansour Hadi – currently hiding out in Riyadh – plenty commented that it was a shame Riyadh couldn't have demonstrated its coalition-building skills in 2011 when the war first broke out in Syria.

The region was then crying out for a pan-Arab response to Assad's barbaric smiting of a popular revolution, and yet none came.

Now, as the Yemen intervention looks increasingly doomed, some argue that it is not too late – and moreover, that it is time to bring Turkey back into the fold. The reports that Saudi Arabia have already began speaking to Turkish president Recep Erdogan about a regional response to the Syrian crisis were greeted as wishful thinking when they were reported earlier this week, but prominent voices in the kingdom have since suggested that a deal is not unthinkable.

Jamal Khashoggi, a prominent and well-connected Saudi journalist, took to Twitter earlier this week to argue that talks between Saudi Arabia and Turkey over Syria were indeed taking place.

Soufan argues that the advantage of focusing on Syria is that it is an issue around which the Sunni partnership can coalesce. Saudi Arabian King Salman bin Abdul-Aziz is less obsessed with the Muslim Brotherhood than his predecessor, but more concerned with building a strong Sunni alliance that reaches out to non-Arab States, in particular Turkey and Pakistan.

While many Arab and Muslim nations committed to contributing ground troops in the early days of the Yemen crisis, most have now pulled out. Pakistan have publicly said they will not and Egypt's commitments never really seemed feasible – not least because of that country's bloody history of intervention in the civil wars of the Arabian Peninsula's most southerly state.

Turkey would be unlikely to even consider an active involvement in Yemen.

"Syria is different. Turkey seems increasingly ready to commit ground troops there if it can have the necessary air cover—something that the US has so far refused to provide," Soufan posited.

It believes that a Saudi coalition with the tacit agreement and indirect support of the US could provide air support for a Turkish military intervention, initially on humanitarian grounds but poised to extend its role.

Barnes-Dacey agreed that Turkey's response to the Syrian civil war so far has been largely due to a reluctance on the part of the US to take ownership of the crisis. But like Saudi Arabia, Erdogan would like to see a more assertive approach. Turkey has already been much more active in preventing Isis fighters from crossing into Syria from its territory in recent months.

"The Turks would welcome the Arab league [taking] a more assertive policy. They don't want to do it single-handedly or to lead an intervention. Erdogan is invested in seeing Assad gone and if the Saudis were prepared to put money and commitment into that effort they would certainly back it," he said.

In this scenario, Saudi Arabia, Turkey and other Sunni Arab states would negotiate a ceasefire that would see the removal of Assad and a peace deal that was sell-able to both Hezbollah and other moderate Sunni forces in the country. Soufan argued that both Russia and Iran would likely accept the removal of Assad, providing a moderately pro-Iranian - or at least not anti-Tehran - regime remained in place.

"If it is possible to take [Assad] and close supporters out of key positions without collapsing the whole edifice that would be an objective worth striving for. Once achieved, all forces could then turn their attention towards the so-called Islamic State, and test their degree of influence over the extremist agendas of other groups," the group argued.

Barnes-Dacey is more sceptical about Iran tolerating a coalition of Sunni states seeking to unseat Assad, a traditional ally to Tehran for whom one of its most prominent proxies, Hezbollah, are currently fighting. If the last four years have demonstrated anything it is that Tehran is willing to back its regional allies in a substantial and organised way.

"To think that the Saudis are going to suddenly out-manoeuvre the Iranians is a long shot. As is the idea that any semblance of unity between Sunni states is going to hold," he said.