SBS News looks back at eight years of conflict in Syria.
How did the conflict start?
In March 2011, a teenager spray painted a message on a wall in the Syrian city of Daraa.
"It's your turn doctor," it read.
The vandal was referring to the country's president, Bashar al-Assad, a British-trained ophthalmologist, or eye doctor. It was his 'turn' to lose power in the Arab Spring in a wave of uprisings spreading across the Middle East.
In response, the Syrian government rounded up more than a dozen children - as young as 10, some say - and held and tortured them for weeks to find out who was responsible.
The act came to symbolise the repressive and often brutal rule of Assad, sparking protests from relatives, neighbours and hundreds of others in Daraa.
When Syrian security forces opened fire on crowds protesting the government's actions, events escalated quickly. The government's crackdown only led to more unrest, radicalising citizens who formed rebel groups. It also led foreign fighters who opposed to Assad to flood into the country.
That was the start of a brutal civil war which has evolved and since killed hundreds of thousands of people, caused millions more to flee, and contributed to the rise of Islamist terror groups such as IS.
Who's fighting who?
One of the most prominent of the early groups fighting against the government was the Free Syrian Army. They were a group led by several former army officers and formed months after the initial protests.
The main opposition group at the time, representatives said they were a secular group committed to bringing democracy to Syria.
After years of war, the "army" wing of the Free Syrian Army has all but fallen apart. It is now more of a loose group of rebel militias fighting under the same banner and sharing limited resources.
Those groups aren't the only ones on the ground, there are many other rebel forces, ranging from moderate fighters to hard-line Islamists.
IS at one stage controlled most of eastern Syria, but rival campaigns by the government and the foreign-backed forces took almost all its territory.
Baghuz, located on the Euphrates River in eastern Syria near the border with Iraq, is the last significant territory still in the hands of IS.
And US-backed forces are now conducting a ferocious assault on the area in a bid to quash them.
But IS still operates in remote territory elsewhere and it is widely assessed that it will continue to represent a potent security threat.
Then there's another player, the Kurdish forces.
Around 30 million Kurdish people also live in the region which straddles the borders of Turkey, Iraq, Syria, Iran and Armenia.
For more than 100 years, the group has aspired to form its own state, and in the wake of the instability, Kurdish groups have been fighting to retain control of their territory.
To complicate things further, some of these forces are not only fighting against Assad, but also against each other.
Meanwhile, Assad's goal is clear: the complete recapture of all parts of Syria and the restoration of his government's rule.
Human rights groups have reported widespread atrocities committed by almost all parties, including the use of child soldiers.
How are other countries involved?
Because of Syria's size, location, and air and sea access routes, the country is of high strategic importance to other nations. Consequently, several foreign players have become involved in the conflict.
One of Assad's strongest allies is Russia. It turned the war in his favour by sending its air force to help him in 2015.
At its weakest point in 2015, Assad's government controlled less than a fifth of Syria. But since Russia entered the war on its side, it has reclaimed huge swathes of the country.
Assad's other main backer is Iran, along with allied militias such as Hezbollah from Lebanon. Tehran says it is fighting anti-Shi'ite Sunni militancy. But Iran's critics say it wants to cement regional power with a "land bridge" extending from Iran through Iraq and Syria to Lebanon.
Turkey’s role is as confusing as the conflict itself. It has been one of the biggest supporters of the anti-Assad rebels, but only the non-Kurdish ones. Turkey, which has a restive Kurdish population, staged incursions into Syria in 2016 and 2018 ostensibly to stop Kurdish forces gaining a foothold on the border.
Turkey has helped the rebel groups it supports to form a local administration and police force, set up schools and hospitals and has installed branches of its own postal system and other public services.
The US helped anti-Assad rebels earlier in the war then became more focused on fighting IS. It backs the Syrian Democratic Forces alliance, whose strongest element is mainly-Kurdish militia the Kurdish YPG (or People's Protection Units). But Washington has attempted to sooth the outrage this has caused its NATO ally Turkey.
Washington also wants to contain Iran as it sees the country's growing influence across the region as a threat to its closest Middle East allies Israel and Saudi Arabia.
Following a request from then-US president Barack Obama in 2015, the Australian government joined the US and other coalition partners in bombing raids against IS in Syria.
Israel wants to stop any expansion of power for its foes Iran and Hezbollah and keep them far from its borders.
How bad is it?
The Syrian war has escalated beyond what anyone could have imagined when the government detained that group of children in 2011 over the graffiti.
The Syrian Observatory for Human Rights said by the end of 2018 it had recorded the deaths of 367,965 people, nearly a third of them civilians, since protests erupted in March 2011 against Assad.
The group says the war has killed 111,330 civilians, including more than 20,000 children and more than 13,000 women.
More than 124,000 pro-government fighters have died, around half of them regime troops and the rest an assortment of Syrian and foreign militiamen loyal to Assad.
According to the United Nations, the conflict has produced more than 5.6 million Syrian refugees and 6.1 million internally displaced people.
"More than 13 million people inside Syria require humanitarian assistance, including nearly six million children," UN material says.
Human rights abuses have been serious and widespread, according to rights groups.
Human Rights Watch says that armed groups have mounted deliberate and indiscriminate attacks on civilians, using child soldiers, and torturing prisoners.
The government is guilty of disappearances, torture, arbitrary arrest, and allowing numerous deaths in custody, they say. It stands accused of repeatedly using chlorine, sarin gas and barrel bombs on its own civilians.
In the battle for the rebel stronghold of Aleppo, the UN raised concerns of widespread war crimes on all sides - including indiscriminate targeting, government use of chemical weapons and rebel use of human shields.
The humanitarian fallout has also had a significant impact on surrounding countries, with Lebanon now home to over one million Syrian refugees – who make up as much as 20 per cent of the country's current population.
Using its control of regions of Syria and Iraq as a base, IS spread its propaganda and violence not only within the country around the world.
The crisis has generated hundreds of thousands of official asylum applications in the European Union, while thousands more have attempted to reach Europe by land and by sea.
The EU migrant crisis has become a major challenge for the open-border political union, with migration said to be the major driver behind the Brexit vote and the rise of right-wing parties across the continent.
How will the conflict end?
Marking the eight years of conflict, UN Secretary-General António Guterres said "more than 11 million people inside Syria need humanitarian aid. Many face violence on a daily basis".
And UNICEF Executive Director Henrietta Fore said "today there exists an alarming misconception that the conflict in Syria is drawing quickly to a close – it is not".
"Children in parts of the country remain in as much danger as at any other time during the eight-year conflict," she said, adding that 2018 was the deadliest year yet for children since the start of the war.
"The year 2018 also saw 262 attacks against education and health facilities, also a record high."
And while Assad and his forces have regained a significant amount of territory, this does not mean the end of the conflict is in sight.
Lots of territory is beyond Assad's grip, including the province of Idlib, where a temporary truce came into force in September.
A large chunk of northern and eastern Syria also remains outside his control. This territory, rich in oil, water and farmland, is held by Kurdish-dominated fighters supported by US forces.
While the Kurds are not hostile to Assad, they want a large degree of autonomy, which he opposes.
As such, many see a negotiated political solution as the only realistic outcome.
But with so many divergent groups and so many external vested interests, getting everyone to the table and keeping them there is proving difficult.
Additional reporting: AFP, Reuters