- Conflict began as an anti-government uprising on March 15, 2011
- More than 220,000 people have been killed
- Half of the country's population is displaced
- Country has been carved up by army and rebel groups
Syria's conflict has entered its fifth year with the government emboldened by shifting international attention and a growing humanitarian crisis exacerbated by the rise of the Islamic State of Iraq and the Levant (ISIL).
More than 220,000 people have been killed and half of the country's population displaced, prompting rights groups to accuse the international community of failing Syria.
On Sunday, media activists in the town of Douma in northern Damascus reported that more than 30 people, including chidren, were killed after government warplane launched air strikes targeting residential areas and schools.
The country has been carved up by government forces, armed groups, Kurdish fighters and other rebel groups.
View all of our coverage marking the fourth anniversary of Syria's conflict
Diplomacy remains stalled , with two rounds of peace talks achieving no progress and even a proposal for a local ceasefire in Aleppo fizzling out.
The conflict began as an anti-government uprising, with protesters taking to the streets on March 15, 2011, inspired by similar revolts in Egypt and Tunisia.
But a government crackdown on the demonstrations prompted a militarisation of the uprising and its descent into today's multi-front conflict.
"Nobody really expected that we would reach this stage in which we will actually be having this national disaster in Syria," Marwan Kabalan, a Syrian academic and analyst at Doha Institute, told Al Jazeera as the conflict entered its fifth year on Sunday.
"The heavy-handed approach that was used by the regime against the peaceful protesters was the main reason that this fairly peaceful revolution has turned into the sort of conflict that we are witnessing right now."
The consequences have been devastating.
The UN refugee agency UNHCR says Syria is now "the biggest humanitarian emergency of our era".
Around four million people have fled abroad, with a million and a half taking refuge in neighbouring Lebanon.
Al Jazeera's Zeina Khodr, reporting from the Bekaa Valley refugee camp in Lebanon, said many have "lost hope" that the civil war would end soon.
|There are a million and a half refugees who have fled Syria and are now living in neighbouring Lebanon [Al Jazeera/Diana Al Rifai]
"When you talk to people here, they have lost faith in the international community," she said.
She also said that many have been angered by the statement of John Brennan, director of the Central Intelligence Agency, who said the US does not want a chaotic fall of the Assad regime, because it is worried "that extremists would take power".
"For people here, how they understand this is that the world wants to keep President Assad in power," she said.
Inside Syria, more than seven million people have been displaced, and the UN says around 60 percent of the population now lives in poverty.
The country's infrastructure has been decimated, its currency is in free fall and economists say the economy has been set back by some 30 years.
Torture and detentions
Rights groups have documented horrific violations, with the Britain-based Syrian Observatory for Human Rights reporting this week that 13,000 people had been tortured to death in government detention since the uprising began.
Tens of thousands more remain in regime jails and detention facilities, with many effectively disappearing after their arrest.
Read more - Syria is dead, long live the Syrians
Despite international outrage at the death toll, and allegations that his regime used chemical weapons against its own people in August 2013, President Bashar al-Assad has clung to power.
His forces have consolidated their grip on the capital Damascus and are moving to encircle rebels in the second city of Aleppo to the north.
Despite the international attention, there is little prospect of a peaceful resolution of the conflict.
Two rounds of UN-sponsored talks in Switzerland failed to achieve progress, and Staffan de Mistura, the third UN envoy to tackle the conflict, has gained little traction with his proposal for a localised ceasefire in Aleppo.
Russia, a key Assad ally, is floating its own dialogue process, and will host talks in Moscow in April, but it remains unclear if the internationally recognised opposition will attend.
The United States said on Sunday it will have to negotiate with President Assad for a political transition in Syria and explore ways to pressure him into agreeing to talks.
US Secretary of State John Kerry said: "We have to negotiate in the end. We've always been willing to negotiate in the context of the Geneva I process" - referring to a 2012 conference which called for a negotiated transition to end the conflict.
"What we're pushing for is to get him [Assad] to come and do that, and it may require that there be increased pressure on him of various kinds in order to do that," Kerry said.
Source: Al Jazeera and agencies