Q: How did the uprising begin?
The arrest and torture of a group of around 15 children for painting anti-government slogans on a school wall sparked a wave of protests in the southern city of Deraa in March 2011. These escalated when security forces killed a number of demonstrators. The ensuing unrest spread across the country and led to calls for President Bashar Assad's resignation.
Q:What happened next?
The government sent tanks into Deraa to crush the uprising and its crackdown became increasingly vicious. In 2012, fighting reached the capital, Damascus, and the city of Aleppo. Last February, rockets and mortars rained down on Homs where the Baba Amr region - a rebel stronghold - became a focal point for the unrest. Subsequent assaults from both sides have led to an estimated 100,000 deaths.
Q:Who are the rebels?
Various political groups, activists, militants and dissidents are united by their desire to oust Assad. But the striking lack of unity among the predominantly Sunni opposition has left it unable to agree on how this can be achieved. A chronic lack of resources has further disadvantaged the rebels. The Free Syrian Army (FSA), a group of early army defectors, is one of the most prominent rebel groups. It describes itself as an "army for all" and claims to be non-sectarian, unlike other opposition branches such as the Syrian Liberation Front or the Syrian Islamic Front, which espouse Islamist ideology. Extremist elements within the opposition movement are believed to have links with al Qaida.
Q:Who has backed the rebels?
As the death toll climbed, foreign nations began siding with the rebel groups. They received logistical support from Western countries and Gulf Arab states sent money for weapons. Last May the EU restricted the supply of weapons used to quash demonstrations. Britain and France asked the EU to reconsider the arms embargo in March, hoping to bolster the rebels' campaign. In June the White House announced the US would supply direct military aid to the Sunni Muslim opposition and Britain is now considering similar intervention.
Q:Who has backed the government?
Russia has supplied Assad's regime with arms. Its president Vladimir Putin raised tensions on a recent visit to London when he warned Britain not to try to arm Syrian rebels who "eat the organs" of their enemies. Iran is said to be "committed to preserving" Assad's regime and was reportedly set to send 4,000 Iranian Revolutionary Guards to the war-ravaged country in June, in support of government forces.
Q:Have civilians been targeted during the conflict?
Security forces have been accused of deliberately targeting civilians. More than 100 people - around half of them children - died in a massacre in the village of Houla last May. Reports suggested many victims were shot in their homes following a demonstration against the government.
Q: Are chemical weapons involved?
Syria is thought to have some of the world's largest stocks of chemical weapons - including mustard gas and the nerve agent sarin. Reports suggest the latter was involved in the deadly attack on a suburb of Damascus last Wednesday. Many of the victims had extreme breathing difficulties in the aftermath of the assault while few showed signs of blood or flesh wounds. Images show men suffering convulsions and foaming at the mouth. Assad firmly denies claims that his regime has used chemical weapons, suggesting that opposition forces could be responsible.
Q: How many people have died in the conflict?
UN estimates suggest more than 100,000 people have been killed so far. Around 30 aid workers are believed to have died during the crisis. Sunday Times journalist Marie Colvin was among a number of reporters killed in Syria. Ms Colvin, 56, died in a rocket attack in Baba Amr, alongside French photographer Remi Ochlik, 28, last February.
Q: How serious is the humanitarian crisis?
Estimates suggest more than two million people have been forced to flee their homes - of which a million are believed to be children. Hundreds of thousands of people have fled to neighbouring countries such as Jordan, Lebanon, Iraq and Turkey. Millions more have been offered humanitarian aid in Syria where violence has made it difficult for many to access food, water, electricity and medical supplies. Human rights groups expect more then three million Syrians will have left the country by the end of the year, if current trends persist.
Q: Could troops be used to create and guard 'safe zones'?
The creation of so-called "buffer" or "safe zones" would see some of Syria's borders with neighbouring countries used to create makeshift camps for refugees. However, such zones would require stringent efforts to defend the camps from air, missile and ground attacks. Some countries may be unwilling to see such a zone established on their border with Syria, through fear the violence will spread closer to their land. Some neighbours, such as Turkey, already feel as though the conflict is heavily involving their country.
Q: Would a no-fly zone restrict air strikes?
The Assad regime has meted out violence both from ground level through tanks and shells, as well as air strikes. An allied forces-enforced no-fly zone has been suggested as a means of preventing the bombing of large swathes of civilian population, as well as aiming to reduce air strikes on rebel bases. Yet they could be difficult to enforce, and are deemed "insufficient" alone in restraining regime forces without targeting ground forces as well. Russia has already said any attempt to enforce a no-fly zone over Syria from Jordan would violate international law.
Q: Should the military target Syria's weaponry?
Syria is thought to have some of the world's largest stocks of chemical weapons, including mustard gas and the nerve agent sarin, although the government in Damascus has refused to confirm it. The regime is believed to hold significant quantities of these in reserve, scattered at bases throughout the country - one of the few in the world not to have outlawed the use of chemical weapons. Targeting and either destroying or securing the stock would prevent it being used on civilians or by terrorists, though the fact that little is known about where it is stored would make finding it extremely difficult. The sheer number of military personnel required to complete the operation could also make it hard to carry out.
Q: Would President Assad be targeted?
He was recently the subject of an assassination attempt, though the attack on his motorcade ended up injuring only Assad's bodyguards. Military experts reckon Western forces would be more likely to go for other regime targets so as not to influence the outcome of a civil war through taking out Assad.
Q: What are the dangers?
Sending an influx of British, American or other Western troops to Syria - or indeed other parts of the Arab world - would undoubtedly attract enemy attacks, including raising the prospect of suicide bombings. It is more likely that air launch missiles would be deployed in order to reduce the risk of military casualties.
Q: What stumbling blocks could hinder international involvement?
Efforts to achieve United Nations backing for any British military action against Assad would be hampered by the opposition of Russia, which could veto any resolution against its ally. The split over the use of chemical weaponry, and whether Assad has been responsible, is characterised by the fact David Cameron and his Russian counterpart Vladimir Putin continue to clash over evidence of such an attack. Assad denies using the weapons and Moscow - a key regime ally which supplies arms to Syria - has backed claims that video footage of victims could be opposition propaganda. Going to war without a UN mandate has already concerned Barack Obama.
Q: What hopes are there of military action being successful?
Some Western analysts say any action against Syria would be "symbolic and punitive". But any operation in the heartlands of Syrian conflict would be fraught with difficulty - the UN having confirmed that chemical weapons experts, who were trying to investigate a deadly attack blamed by Western nations on Assad's regime, have been "deliberately shot at multiple times" in Damascus. Shocking images beamed around the globe in recent days have shown, in graphic detail, the cost that a chemical attack has on the human body.