Chaotic mix of actors and interests in Syria war17 february 2016, 16:41
Syria's brutal five-year war has turned increasingly messy, threatening a broader regional conflict as a tangle of internal and external players push their own multi-faceted agendas, AFP reports.
Who are the key foreign actors and what are their goals?
Russia and Iran are the major backers of Syrian President Bashar al-Assad. Their ultimate objectives differ, but both appear determined to annihilate the opposition and keep the regime in power.
Syria is a key foothold for Russia in the Middle East, an important military staging post from which to project influence across the region. Analysts say Moscow is not necessarily wedded to keeping Assad in power in the long term, but wants to ensure control over any future political transition.
Russia launched its own air strikes in Syria in September to support Assad and fight "terrorists", saying it was targeting the Islamic State group and other jihadists.
But the West has accused Moscow of seeking to eliminate all opposition rebels, including more moderate groups.
The Russian-backed regime assaults on rebel bastions in the northern city of Aleppo that began on February 1 have shifted the momentum decidedly in Assad's -- and Moscow's -- favour.
Advances by regime forces have seen indiscriminate bombing of civilian areas, killing hundreds of people and causing some 50,000 to flee Aleppo.
Tehran has sent thousands of "military advisors" to Syria, including Shiite militias and members of its Lebanon-based proxy force, Hezbollah. Assad has long been a close ally of Iran as part of its battle for regional dominance against the leading Sunni power, Saudi Arabia.
The countries backing the opposition are fractured, often finding themselves at odds even with their allies.
Russia's bulldozer approach to the conflict has caught the West offguard, undermined its repeated calls for a political solution and triggered a virulent reaction from the leading supporters of the rebels -- Turkey and Saudi Arabia.
The war of words has escalated between Moscow and Ankara, already at daggers-drawn since Turkey shot down a Russian fighter jet on the border in November. The West fears the consequences of further aggression between Russia and Turkey -- a NATO member which boasts the alliance's largest military force after the United States.
Turkey -- once a friend of Assad -- now vehemently opposes the Damascus regime, and analysts say it initially saw the conflict as an opportunity to extend Ankara's influence south. But Turkey is now hosting 2.6 million Syrian refugees and trying to keep security in a border region where IS jihadists are active.
Turkey has long rejected claims of aiding IS, which has now carried out string of attacks on its soil.
But it is also increasingly concerned by the growing influence of Kurdish fighters in Syria, fearing they are seeking to carve out an autonomous region on Turkey's border and embolden the homegrown rebel Kurdistan Workers' Party (PKK).
It has carried out air strikes on the Syrian Kurdish militias, even though they are backed by the West as one of the few forces capable of tackling IS.
Officially, Saudi Arabia's main concern has been IS, saying it will increase its air strikes against the jihadists. However, analysts say Riyadh is primarily interested in supporting opposition rebels as part of its regional competition with Iran, which has also seen it battle Iranian proxies in Yemen.
US forces have been bombing Islamic State positions in Iraq and Syria since September 2014, carrying out the vast majority of strikes by the anti-IS coalition.
But despite repeatedly calling for Assad to step down, President Barack Obama has been reluctant to directly back the "moderate" opposition rebels. Having been elected in 2008 on a mandate to pull US forces out of Iraq, he has been unwilling to involve the country in another grinding war in the Middle East even when Assad was shown to have crossed Obama's supposed "red line" of using chemical weapons in 2013.
Washington's efforts to train and equip a "moderate" rebel force to take on IS was a spectacular failure in 2015. It struggled to find recruits among the opposition, whose primary concern was fighting Assad, and its first fighters were almost immediately intercepted and disarmed by jihadists, leading to the scrapping of the $500 million programme in October.
The United States has continued to press for dialogue and a political transition, but its critics say this has allowed Russia to seize the momentum with its more ruthless military aggression.
France has been one of the most hostile opponents of Assad, and following the jihadist attacks in Paris in November it has stepped up air strikes against IS.
However, France lacks the military or diplomatic clout to direct Western actions. Outgoing foreign minister Laurent Fabius bemoaned Washington's lack of commitment to the rebel cause when he resigned last week, but his government finds itself powerless to alter the dynamics of the conflict.
By Cécile FEUILLATRE