The conflict in Syria has entered its fifth year, a grim anniversary in what has become the worst humanitarian crisis of our time.
It began on March 15, 2011 when the Syrian government met mostly peaceful protests in several towns and cities with gunfire, beatings and arrest. Eventually, the opposition acquired weapons, soldiers defected, and the uprising transformed into a grinding civil war with ugly sectarian dimensions that sucked in countries across the region and further afield. An estimated 220,000 people have now been killed and life expectancy has dropped two decades to 55 years, according to the United Nations. 3.9 million people have fled the country, and a further 7.6 million have been internally displaced.
Syria's economy has collapsed and 80 percent of the country now lives in poverty. Half of all school-aged children haven't attended school in three years. The country has literally gone dark, with 83 percent of electricity supplies now cut.
A peaceful solution to the conflict now seems further away than ever, and United Nations Security Council (UNSC) resolutions aimed at pushing President Bashar al-Assad to step down or cease attacking his own people are consistently vetoed by his longtime allies Russia and China. Moderate rebel factions fighting for a democratic system have lost out to Islamist-linked groups and the chaos has allowed extremist militants such as the so-called Islamic State (IS) to seize territory and power.
Arab Spring-inspired unrest begins after police arrest fifteen young boys in southern town of Daraa for spray-painting "the people want the downfall of the regime" on buildings. Large demonstrations take place in Damascus, Daraa and elsewhere to demand the release of political prisoners and Assad's resignation.
Unrest spreads and protests continue, including in Homs and Banyas. Some pro-government demonstrations take place too. Security forces attempt to crush dissent, killing dozens. Assad blames foreign powers for the unrest, and announces measures designed to placate protesters, including allowing new political parties and a potential end to a state of emergency that has been in place for 48 years. Opposition members say the measures are superficial and don't constitute meaningful reform.
Protests demanding Assad's ouster spread further. The government's response becomes more brutal and Assad vows to destroy what he describes as "terrorists." Hundreds are killed, including more than 120 at "Bloody Friday" protests in Daraa, Damascus and elsewhere. The United States and France condemn the crackdown and call on Assad to implement reforms.
In an attempt to calm unrest, the government releases some political prisoners and repeals the emergency law. The first Syrian refugees cross into Turkey, where authorities build the first of 20 Syrian refugee camps to provide them with shelter.
Syrian army tanks are deployed in Daraa, Homs, Banyas and the Damascus suburbs in an attempt to put down the protests.
The US imposes sanctions on both Assad and senior Syrian government officials, while the European Union implements an arms embargo alongside an asset freeze and travel ban on senior officials.
Reports emerge of Iran providing assistance and equipment to help quell the uprising. Tehran later provides arms and combat troops to bolster Assad.
The crackdown continues, including 34 killed at huge anti-government demonstration in Hama. The Arab League condemns the Syrian government's actions.
More than 120 soldiers are killed in Jisr al-Shughour by what Damascus describes as "armed gangs," but some reports suggest the attack was carried out by defected members of the security forces and local residents. The army besieges the city and thousands of civilians leave their homes and seek refuge in Turkey.
The burgeoning conflict spills over into Lebanon as pro and anti-Syrian government factions clash in Tripoli. Assad pledges to start a "national dialogue" on reform.
After a massive demonstration in Hama, Assad removes the provincial governor from power and deploys troops. Hundreds are reported killed in the city.
The government holds a national dialogue, which is boycotted by opposition groups. The US says Assad has "lost legitimacy".
Military defectors announce the formation of the Free Syrian Arm (FSA) headed by Riad Al-Asaad, a former Syrian army colonel.
International condemnation grows. The UK, US, European Union and others demand that Assad steps down. The UN condemns human rights violations and the use of force against civilians. Saudi, Bahrain and Kuwait recall ambassadors.
Formation of the Syrian National Council in Istanbul, a coalition of groups in and outside the country opposed to Assad.
The European Union bans oil imports from Syria following the US's decision to do the same the previous month. Turkey, a former ally of Assad, cuts contact with Syrian authorities. Fighting between the Syrian military and defected troops continues.
The UN Security Council (UNSC) attempts to pass a resolution condemning Assad's government. Russia and China veto it. Meanwhile, UN High Commissioner for Human Rights Navi Pillay says the crisis shows signs of "descending into an armed struggle." Clashes take place in Homs and government troops shell the city.
The Arab League announces a peace plan. Damascus accepts but does not adhere. The Arab League take the unprecedented step of suspending Syria and imposes sanctions.
The FSA attacks a military base near Damascus, in the highest profile assault yet. Pro-government Syrians attack foreign embassies.
Syria agrees to admit Arab League observers to monitor compliance with an agreement by which the government pledged to pull troops and heavy weapons out of civilian areas and allow access to journalists and human rights workers. Security forces fire on an anti-government demonstration in Hama the day before the observers arrive.
200 are reportedly massacred in Idlib province by security forces, while a double suicide car bomb attack close to the intelligence headquarters in Damascus kills more than 40. The UN says 5,000 have died since the beginning of the uprising.
The Arab League calls for Assad to step down and withdraws its observers due to increasing violence.
Jabhat al-Nusra announces its formation as Syria's official al-Qaeda affiliate. The group's mainly local fighters prove to be effective against the regime and an initially ally with more moderate groups.
The UNSC tables a draft resolution supporting an Arab League call for Assad to step down. Russia and China veto it. The UN General Assembly votes to condemn human rights abuses and also demands Assad's resignation. Kofi Annan is appointed Joint Special Envoy of the UN and Arab League to the crisis.
The bombardment of Homs and other cities intensifies. Hundreds die. Government controlled areas vote on a new constitution establishing a multi-party system. The polls are widely derided as a sham.
The US closes its embassy due to security concerns. Al-Qeda head Ayman al-Zawahiri calls for militants across the region to join the fight against Assad.
More than 7,500 have died in the conflict, the UN says.
A year after the uprising began, six Gulf states close their Syrian embassies. The UNSC endorses Kofi Annan's non-binding peace plan, which is softened to secure Russian and Chinese backing. It fails and violence continues.
Syrian troops push into Homs and retake what little is left of Bab Amr district. The FSA had pulled out previously, unable to hold the area against better armed opponents and citing fears for civilian safety.
Annan brokers a ceasefire that Assad's government pledges to comply with. UN observers are deployed. Assad says he has regained control over the country, but rebels accuse government forces of continued abuses and massacres.
The international Friends of Syria coalition convenes in Istanbul and votes to recognize the Syrian National Council. The US pledges to provide communications equipment to rebels and Arab states promise $100 million.
More than 100 people, almost half of which are children, are killed in the village of Houla. A subsequent report from the UN Human Rights Council accuses Assad's troops and allied "shabiha" militias of war crimes and condemns the use of heavy weapons on civilians. A number of European countries and Australia expel Syrian diplomats.
More than 50 people die in a suicide attack on a Damascus police base.
Parliamentary elections are held but boycotted by the opposition. The vast majority of seats go to Assad or his allies.
The UN suspends observer patrols due to the deteriorating security situation. There are renewed calls for the peace plan to be implemented, but Assad tells his new government that the country faces "real war."
UN officials first begin to describe the crisis as a civil war. A Syrian air force pilot defects to Jordan, while a Turkish F-4 phantom reconnaissance jet that strayed into Syrian airspace is shot down by Syrian forces. The incident escalates tensions between the two countries, and Turkey subsequently changes its rules of engagement and says that Syrian troops deployed near Turkish borders would be considered a threat.
A bomb attack on the National Security building in Damascus kills defence minister Daoud Rajha and his number two Assef Shawkat, who is also Assad's brother-in-law. The FSA claims responsibility and say it was retaliation for an internationally condemned massacre in Tresmeh village that left 200 dead.
There are a number of high profile defections from Assad's government.
The UNSC tables a resolution threatening sanctions against the Syrian government. Russia and China veto it. Assad says he will use chemical and biological weapons if Syria is attacked by a foreign power.
Rebels take control of eastern Aleppo, setting the scene for one of the most bitterly fought battles of the conflict. A government offensive fails to dislodge them.
UNHCR-run Zaatari refugee camp is opened in Jordan. It eventually becomes home to more than 80,000 displaced Syrians.
Annan resigns after proving unable to negotiate a ceasefire. He blames Assad's refusal to adhere to the plan, UNSC friction and the armed rebellion for this failure. He is replaced by Lakhdar Brahimi. Security forces reportedly kill 400 in a Damascus suburb. The UN says both government troops and rebels have committed crimes against humanity
US President Barack Obama says that if the Syrian government uses chemical of biological weapons it will be a "red line" to which America may respond militarily.
Syrian military jets bombs Azaz close to the Turkish border, killing 40.
The US says it will supply rebels with $45 million worth of non-lethal aid.
Syrian forces fire a mortar that lands in the Turkish border town of Akcakale and kills 5 civilians. Turkish troops return fire.
Aleppo's historic market is badly damaged by fire as fighting continues.
The National Coalition for Syrian Revolutionary and Opposition Forces is formed is after a meeting in Qatar, although Islamist factions, including Jebhat al-Nusra, say it does not represent them.
The UN says rebels may have committed war crimes by summarily executing captured soldiers.
Israeli forces fire on Syrian positions after sporadic shelling from across the Golan heights.
Salim Idris replaces Riad Al-Asaad as FSA head. Rebels make gains in Damascus, taking a number of military bases and pushing towards the airport.
The US labels Jabhat al-Nusra a terrorist organization and says the Syrian National Coalition is the legitimate representative of the Syrian people. The UK, Turkey, France and Gulf States also recognize the coalition.
More than half a million Syrian refugees have fled their homeland by year's end, UNHCR says.
Assad says he will introduce political reforms to end the war.
Violence continues with bombings in Aleppo and Damascus.
The US says it will provide rebels with $60 million worth of medical supplies and food despite National Coalition requests for military aid.
Aa convoy thought to be carrying advanced anti-aircraft weapons destined for Lebanese Shia militia Hezbollah is hit by airstrikes. Israeli forces are widely suspected to have conducted the attack, although there is no official confirmation. Syria says Israel bombed a "scientific research center".
A bombing in Damascus close to Assad's Baath Party headquarters kills dozens.
Rebels continue to make gains, in part thanks to increases in foreign weaponry.
The UN says more than a million Syrians are now refugees. the US and UK say they will provide non-military aid to armed opposition groups and push to lift the EU arms embargo for rebels.
National Coalition head Moaz Al-Khatib resigns and the Arab League gives Syria's seat to the National Coalition. American-educated Ghassan Hitto is elected interim prime minister.
The are increasing reports of Jabhat al-Nusra's attempts to implement Islamic Law in the areas it controls.
Foreign jihadis grow in number and influence with the appearance of the Islamic State. Formerly the Islamic State of Iraq, its leader Abu Bakr al-Baghdadi, announces in an audio message that Jabhat al-Nusra was an extension of his group and would be merged with it. Al-Nusra leader Abu Mohammad al-Joulani spurns their advances.
Hezbollah leader Hassan Nasrallah says Shiite fighters from his group are supporting Assad.
Syrian Prime Minister Wael Nader Al-Halqi narrowly escapes an assaination attempt.
The US pledges $123 million more in non-lethal aid, while the UK and France tell the UN that Assad may have used chemical weapons against opposition-held areas.
George Sabra succeeds Moaz al-Khatib as National Coalition chair.
A shipment of advanced Fateh-110 surface-to-surface missiles from Iran is hit by airstrikes in Damascus. Israel is widely thought to be responsible, believing that they were to be delivered to Hezbollah.
The UN says that 4.25 million Syrians are displaced within Syria.
The conflict spills outside its borders with a double car bombing in the Turkish town of Reyhanli that kills 40, and clashes in Tripoli, Lebanon that leave 10 dead.
Hezbollah chief Nasrallah says his group will back Assad until the rebels are beaten.
The EU lifts its arms embargo on Syrian opposition groups.
The strategically important town of al-Qusair is taken by Syrian troops and Hezbollah.
Rebel commanders complain that they are not being supplied with weapons by the international community because of concerns about the growing Islamist presence in their ranks.
The US deems it "likely" that the Syrian regime has used chemical ordnance on several occasions in the past 12 months, and concludes that direct military support can be provided to rebels. Friends of Syria arrives at the same decision.
The UN calls Syria the "worst humanitarian disaster" since the cold war.
The UN reports that the death toll has now exceeded 100,000. Israeli Defense Forces Military Intelligence Director Aviv Kochavi says Syria has become a "center of global jIhad".
Interim opposition Prime Minister Ghassan Hitto steps down due to his inability to form a government.
Government troops advance in Homs and occupy Khalid Ibn Al-Walid mosque, which had become a symbol for rebel groups.
A Syrian government's siege of the Yarmouk Palestinian refugee camp begins. Well over a 100 people have since starved to death in what Amnesty International has described as a crime against humanity.
A chemical assault on a Damascus suburb kills as many as 1,400 people. The US and others blame the the Syrian government, but it denies the attack and says opposition fighters were responsible. Human Rights Watch (HRW) subsequently concluded that evidence "strongly suggests" Syrian government forces were guilty of using a "weapons-grade nerve agent" likely to be sarin gas in the attack. UN weapons inspectors later say they found "clear and convincing" evidence that rockets containing sarin were used.
Having previously suggested that Syrian chemical weapon use would prompt American use of force against Assad, Obama says he has resolved to take military action, but will seek congressional approval.
UK Prime Minister David Cameron also calls for a military response, but it is blocked in a parliamentary vote.
Russian Foreign Minister Sergey Lavrov question US intelligence on the use of chemical weapons, while President Vladimir Putin issues a warning on the repercussions of US strikes. Moscow then proposes a diplomatic solution to the chemical weapons issue: that Syria signs the Chemical Weapons Convention and allow its chemical weapons to be brought under international control and dismantled. Obama agrees.
Eleven of the biggest Islamist rebel groups reject the National Coalition's authority and declared goal of fighting to create an Islamic state instead.
Organization for the Prohibition of Chemical Weapons (OPCW) officials arrive in Syria to monitor the chemical weapons arsenal dismantlement and later report that the government has made its chemical weapon production facilities inoperable.
A double suicide attack on the Iranian embassy in Beirut kills 23. Meanwhile Islamist rebel factions make gains in Deir Al-Zor province.
Pillay says a UN fact-finding team has amassed evidence suggesting that the Syrian government is complicit in war crimes to the "highest levels."
American and British "non-lethal" aid to rebels is suspended after Islamist groups overrun FSA bases.
By the end of the year, 2.3 million Syrian refugees had fled to Turkey, Iraq, Jordan, Lebanon and Egypt. 18 percent were living refugee camps.
100 are killed in Aleppo air raids.
UN Secretary-General Ban Ki-moon heads the first round of Geneva peace talks, attended by both the Syrian government and National Coalition. No progress is made.
The UN says that it has temporarily stopped reporting death tolls in the conflict due to its inability to verify information.
War Crimes analysts say images and documents smuggled out of the country show prisoners killed on an "industrial scale".
A second round of peace talks begins, but the two sides fail to even agree on an agenda. Joint Special Envoy Lakhdar Brahimi issues an apology for the talks' failure and steps down in May.
Government "barrel bomb" attacks kill almost 250 civilians in Aleppo.
AbdulIlah al-Bashir al-Noeimi replaces Salim Idris as FSA head.
The US National Intelligence Director James Clapper says the war could become a "perpetual stalemate" with no decisive victory possible by either side.
Turkish military shoots down a Syrian MIG-23; Turkish officials say it entered Turkish airspace.
Government forces backed by Hezbollah take Yabroud, the last rebel-held city close to the Lebanese border.
Israel launches airstrikes on Syrian forces after four of its soldiers are wounded in a Golan Heights bombing.
The Jordanian Air Force strikes a convoy on the Syrian-Jordanian border, apparently as it attemps to cross into Jordan. Reports later indicate that it may have been rebels seeking refuge from government troops.
In a symbolic blow for the opposition, government forces retake Homs under the terms of a ceasefire agreement. Both sides agreed on a 48-hour break in the fighting, allowing hundreds of rebels to flee the city's old town where they had been making an increasingly desperate last stand surrounded by Syrian troops.
A HRW report concludes, based on witness interviews as well as video and picture analysis, that Assad's forces have used bombs containing chlorine gas in attacks on rebel-held areas. HRW noted that fragments of chlorine canisters found at the scene indicated that they had been dropped from considerable heights, strongly suggesting that Syrian government forces dropped crude "barrel bombs" containing chlorine from helicopters.
General elections take place in government-held areas. For the first time since the Assad family took power, more than one candidate is allowed, but opposition groups and the international community describe them as a sham.
IS announces a self-declared caliphate with Abu Bakr al-Baghdadi at its head in the territory it controls between Aleppo and eastern Iraq .
The Organization for the Prohibition of Chemical Weapons (OPCW) mission says that it has completed removal of chemical weapons in Syria and that all production equipment and munitions have also been destroyed.
IS consolidates power, including taking a large military base near Raqaa.
The UNSC votes to allow cross-border aid to victims of the conflict in rebel-held areas without prior permission from the Syrian government.
The UN says that IS has committed human rights abuses and atrocities in Syria. The group seizes al-Tabqa air base, the last government stronghold in Raqaa, after fierce fighting. It subsequently massacres over 100 government prisoners.
American journalist James Foley is killed by IS in the first of a number of gory execution videos.
The US assembles an international anti-IS coalition in Paris.
Forces from the United States and five Arab countries launch combined air strikes against IS in Syria.
The OPCW says it had "compelling confirmation" that a toxic chemical, likely pure or mixed chlorine, had been used "systematically and repeatedly" as a weapon in parts of the country where anti-government rebels have been clashing with Syrian President Bashar al-Assad's troops.
IS launch huge assault on Kurdish border enclave of Kobani. The town's defense becomes a symbol of the fight against the group and eventually involves the FSA, coalition airstrikes and peshmerga fighters from Iraq's Kurdish Regional Government.
IS advances into Kobani itself but are pounded by coalition airstrikes. Syrian government forces advance around Aleppo, cutting off main supply lines to the city.
Lebanon closes its borders to Syrian refugees after more than a million people fled there to escape the fighting.
Jebhat al-Nusra pushes Hazm Movement, or Harakat Hazm, out of Idlib province. The secular militia had been supplied with advanced US weapons. Social media accounts linked with Nusra say that US weapons are among a large cache of arms and equipment seized.
NGOs say the international community must do more to help civilians fleeing the Syrian civil war as the financial and social strain of the influx of refugees to Turkey, Iraq, Lebanon and Jordan is overwhelming host countries and some have begun to restrict access to refugees as a result.
The Syrian government says it will now allow the World Health Organization (WHO) to deliver medical supplies to opposition-held parts of Syria previously off limits to aid workers, including Aleppo.
76,000 people died in the Syria conflict in 2014, according to the UN. The deadliest year yet.
Kurdish forces say they have pushed IS out of Kobani.
Reports emerge suggesting that a number of the Syrian rebel groups who had been trained and armed in a covert CIA programme would have their funds and supplies cut or reduced.
The Syrian government says it will suspend airial and artillery strikes on Aleppo as part of a UN proposal.
HRW says Syrian forces continue to use barrel bombs, and have killed and wounded thousands. Assad continues to deny the claims.
The US and Turkey sign deal to train and arm Syrian rebels fighting IS. Hazm announces it will disband after Jabhat al-Nusra captured its Aleppo province headquarters.
Assad says he is tipped off by members of the US-led coalition about airstrikes on IS in Syria, but adds that his government is not directly cooperating with the coalition. IS release video showing a captured Jordanian pilot being burnt alive.
IS suffers a series of defeats in both Iraq and Syria.
Jabhat al-Nusra and other rebels detonate explosives under Aleppo's Air Force Intelligence's headquarters. The group's military chief, Abu Homam al-Shami, is killed, along with three other senior members, in an airstrike.
The UN and a global alliance of agencies, including Oxfam and Save the Children, say 2014 was the worst year of the conflict yet, and accuse members of the international community of failing victims and doing little to mitigate the humanitarian disaster in Syria.