What does the future hold for Syria now the US has halted cooperation with Russia, and why are they involved in the Syrian civil war?
Why the US and Russia are involved in the Syrian war and what lies ahead
The United States and Russia will no longer be cooperating on Syria and that's unlikely to change before the new US administration gets underway, according to Gorana Grgić, a US politics and foreign policy lecturer at Sydney University's United States Studies Centre.
On Monday, the US announced it would halt cooperation with Russia after learning the Syrian government, supported by Iranian-backed militias and Russian air power, had pounded the rebel-held area of Aleppo, and that hospitals had also been hit.
On Friday, US Secretary of State John Kerry called for Russia and Syria to face a war crime investigation as Russia resisted the United Nation's urge for an immediate truce.
Ms Grgić told SBS: “This episode has shown the White House has run out of patience.
"I don’t think we’ll see any reset button being hit in the coming months.”
The lack of will to engage in interstate cooperation is consistent with the long-strained relationship between the US and Russia, she said.
But the move will encourage Syrian President Bashar al-Assad's effort to quell the opposition.
“This certainly gives all the reason to (the) Assad government and his regime to keep pressing on, and try to basically quash the resolve of the rebels to keep on fighting.”
Dr Rodger Shanahan, a Middle East expert at the Lowy Institute think tank, told SBS that the US never really had much influence in the region anyway.
“The US has never had a strong hand to play,” he said. "Russia has always had influence in Syria, whereas US has never really had that.
"They [the US] thought they might have been able to wrest Syria away, but now that hope has evaporated.”
Access to the world
Russia has had access to the Mediterranean through its naval base at Tartus - Russia's only base in the Mediterranean – since Soviet times, which helps it assert its military presence in the region and gives it access to the world, United States Studies Centre’s Gorana Grgić said.
“Anyone who looks at the past year and Russia’s commitment and investment in the civil war in Syria would think that Russia is not going to give up that access that easily.”
The USSR, later Russia, also had a market for arms sales, as the Syrian government was largely dependent on weapons from it.
Some interpret Russia's military effort in the Syrian conflict as a marketing campaign to demonstrate the development of its weapons and equipment in order to attract global sales.
“I would say this isn't irrelevant given that this could help Russia's economy that has been crippled by sanctions and low oil prices.”
Vladimir Putin 'consolidating his rule'
We have to look at Russia's foreign policy assertiveness over the past couple of years, both in Ukraine and Syria, as part of a broader campaign Putin has set out on “to consolidate his rule and deflect from domestic problems,” said Ms Grgić.
“This is something that authoritarian leaders often do, particularly when their rule is being challenged by domestic opposition, as was the case after the presidential elections in 2012, and economic crisis.
“In such cases, creating an external enemy and displaying bellicose behaviour can be helpful in mobilising public support and strengthening the hold on power.”
The United States aims to defeat IS and other terrorist groups in Syria, Ms Grgić said.
“We wouldn’t see this [the US withdrawing from Syria] because of ISIS.
“This is a UN security conflict resolution that basically mandates and gives the task to the international coalition to combat the non-state actors there.”
The US understands there would be “serious implications” if it left. “Obviously in terms of the proliferation of the terrorist groups and the security threat it poses to the Western states.”
She said that the US had more interest in the Asia-Pacific region.
“[The US] doesn’t have a kind of direct interest in Syria and this is what explains the kind of lack of intervention in the first place, this is not a core US interest.
“Certainly, it’s even less interested in the Middle East given the US is no longer dependent on the flow of hydrocarbons from the Middle East.
Ms Grgić also suggested that “having no stake in Syria would open up a lot of space for other states,” possibly giving more sphere of influence to Russia and Iran.
Lowy Institute’s Dr Rodger Shanahan said the war in Syria may remind some people about the 15-year civil war in Lebanon.
“This is just the Lebanon civil war on steroids,” he said.
“But there comes a point where people do become exhausted and do want to kind of get on with their lives.”
Dr Shanahan said he did not believe the Syrian conflict, which began five years ago, will continue for as long as Lebanon’s war, but when it ends, stability “really depends on… whatever post-civil war political solution emerges”.
He also suggested IS there was nearing defeat.
“They’ve lost pretty well all momentum, they’re being constrained in areas, they’re under great pressure in Iraq, they’ve had a series of battlefield defeats and they’ll either collapse spectacularly or just be attrited further and lose their foothold on physical territory.”
Extreme Islamic ideology will not be defeated, but their hold on physical territory will be, he said.
“[Former Islamic State members will] splinter into different groups, in different locations, in different countries.”
Iran views Syria as imperative to its power, according to US foreign policy organisation Critical Threats.
“The fall of the Assad regime would further reduce Tehran’s ability to project power,” Will Fulton, Joseph Holliday and Sam Wyer wrote in a Critical Threats paper titled ‘Iranian Strategy in Syria’.
Iran is a long-standing ally of Syria, providing economic and military support to Bashar al-Assad’s regime. Shi'te militias also support Mr al-Assad while Sunni rebels seeking to unseat him are backed by Turkey and Gulf Arab states.
Mehdi Taeb, a confidante of Iran’s Supreme Leader Ali Khamenei, said in 2013: “Syria is the 35th province [of Iran] and a strategic province for us.
“If the enemy attacks us and seeks to take over Syria or [Iran’s] Khuzestan, the priority lies in maintaining Syria, because if we maintain Syria we can take back Khuzestan.
"However, if we lose Syria, we won’t be able to hold Tehran.”
That same year, Ali Akbar Velayati, a senior foreign affairs advisor to Ali Khamenei, expressed Iran’s interest in Syria by describing it as “the golden ring of resistance against Israel”.
Karim Sadjadpour, a lead Iran researcher at the Carnegie Endowment for International Peace, argued in a Carnegie op-ed that Iran, a Shia-majority Islamic country, fears the fall of the Syrian Shia regime could result in “a Sunni sectarian regime aligned with Saudi Arabia or the US and hostile to Shia Iran”.
Mr Sadiadpour also notes that Syria is vital to Iran because it provides a “geographic thoroughfare to Lebanese Shia militia Hezbollah, “which is one of the crown jewels of the Iranian revolution.
“Both Syria and Hizb Allah are crucial elements of Iran’s resistance alliance.”