Saturday's suspected chemical attack in the Syrian city of Douma has reportedly killed up to 40 people and put new focus on the already seven year-long Syrian Civil War.
The conflict has reportedly claimed the lives of as many as half a million people, caused the worst refugee crisis since WWII, and destroyed so many cities and so much infrastructure that the cost to rebuild is an estimated $200 billion.
What started as street protests turned into a civil war, and has now erupted into a war that involves dozens of nations (directly or indirectly), hundreds of armed groups, and four main sides.
Despite all that, the war continues — and shows no real signs of stopping anytime soon.
Take a look here at how the conflict unfolded:
Veronika Bondarenko contributed to a previous version of this story.
In the spring of 2011, a series of pro-democracy protests known as the Arab Spring were rocking countries across the Middle East. In Syria, people peacefully protested in the streets after President Bashar Assad's government arrested and tortured teenagers for writing pro-revolution graffiti on their school wall.
A child uses a megaphone to lead others in chanting Free Syrian Army slogans during a demonstration in Aleppo, Syria. (Andoni Lubaki (Associated Press))
To quell the protests, government forces started opening fire during marches and sit-ins. With hundreds of people now killed by Assad's government, the protesters who initially called for more civil liberties started demanding a total overthrow of Assad's regime.
A Free Syrian Army fighter carries his weapon as he smokes a cigarette near the frontline of Otaiba, in al-Ghouta region in the eastern rural suburbs of Damascus, August 15, 2013. (AP)
Source: The Guardian
With no end to the violence, some former government officers formed the Free Syrian Army to support the opposition. Other armed groups with various ideologies and loyalties would also be created. As sides battled for control over major cities such as Homs and Aleppo, the fighting escalated into a full-blown civil war by the end of 2011.
A Free Syrian Army fighter carries his weapon as he smokes a cigarette near the frontline of Otaiba, in al-Ghouta region in the eastern rural suburbs of Damascus, August 15, 2013. (REUTERS/Mohamed Abdullah)
By 2012, fighting between rebel groups and government forces had spilled into the streets, killing and displacing thousands.
Forces loyal to Syria's President Bashar al-Assad walk past damaged buildings in the government held Sheikh Saeed district of Aleppo, during a media tour, (Omar Sanadiki/Reuters)
As the war continued, Assad's government is believed to have started using highly toxic chemical weapons to strike densely populated areas. More than 1,000 people died in a 2013 sarin gas attack on the Damascus suburb of Ghouta, which crossed former President Barack Obama's now-infamous "red line" and led to a deal brokered with Russia to destroy Assad's declared chemical weapons stockpile.
Resident carries an injured man through a site damaged from what activists said was an airstrike by forces loyal to Syria's President Bashar al-Assad on the main field hospital in the town of Douma, eastern Ghouta in Damascus October 29, 2015. (Reuters)
Source: Business Insider and Washington Post
Assad's government started using heavy artillery and barrel bombs — barrels filled with explosives and materials like shrapnel and nails and then dropped from helicopters — to quell the opposition, which led to even more deaths in both rural and urban regions.
Residents carry an injured man at a site damaged by what activists said was a barrel bomb dropped by forces loyal to Syria's president Bashar Al-Assad in Maarat Al-Nouman, south of Idlib June 8, 2015. (REUTERS/Khalil Ashawi)
2016 took a great toll on Syria's children, many of whom have been killed, separated from their families or stranded in refugee camps.
Migrants' children wait to cross the border from Slovenia into Spielfeld in Austria, February 16, 2016. (REUTERS/Leonhard Foeger)
Source: UNICEF and Business Insider
By 2017, over 450,000 Syrians had been killed in the war. "The level of human suffering that I am witnessing with the Syria crisis is indeed without a parallel," said UN High Commissioner Antonio Guterres.
Men rescue a boy from under the rubble after what activists said was explosive barrels dropped in Aleppo by forces loyal to Assad. (REUTERS/Hosam Katan)
Source: I Am Syria and Al Jazeera
Years of fighting also fueled the rise of Islamic extremists like ISIS and al-Qaeda affiliate Jabhat al-Nusra, who capitalized on the turmoil by taking over large sections of Syria and Iraq.
Militant Islamist fighters waving flags, travel in vehicles as they take part in a military parade along the streets of Syria's northern Raqqa province, June 30, 2014. (Reuters)
As Bashar al-Assad lost ground to rebels and terrorist groups, Lebanon's Hezbollah militant group entered the war on the side of Assad. Thousands of Hezbollah militants came across the border and fought ISIS and rebels.
Lebanon's Hezbollah members carry Hezbollah flags during the funeral of their fellow fighter Adnan Siblini, who was killed while fighting against insurgents in the Qalamoun region, in al-Ghaziyeh village, southern Lebanon May 26, 2015. (Reuters)
Source: Modern Diplomacy
Israel, worried that Iran would give Hezbollah advanced weapons, conducted numerous strikes on the group, and other Iranian targets in Syria. Though Israel never confirms or denies its role, there are fears as to how Hezbollah, Iran, and Syria will respond when the war is over.
An Israeli air force F-16s of the flying dragon 115 squadron takes off from Ovda airbase near Eilat, southern Israel, during the 2017 Blue Flag exercise Nov. 8, 2017. (AP Photo/Ariel Schalit)
Source: Washington Post
As fighting continued to devastate the Middle Eastern nation, the conflict escalated into a proxy war between the US, Russia, and Iran. While the US decried Assad's government and supported "moderate" rebel groups fighting the regime, Russian airstrikes and Iran-backed militias bolstered Assad's army.
As fighting continued to devastate the Middle Eastern nation, the conflict escalated into a proxy war between the US, Russia, and Iran. While the US decried Assad's government and supported "moderate" rebel groups fighting the regime, Russian airstrikes and Iran-backed militias bolstered Assad's army. (Russian Defense Ministry)
Source: Reuters (map) and Al Jazeera
Both Assad's government and rebel groups were responsible for grave human rights abuses, a UN report found.
Residents help a man out of rubbles after what activists said was an air strike by forces loyal to Syria's President Bashar al-Assad in Douma, eastern Al-Ghouta, near Damascus, March 7, 2015. (REUTERS/Bassam Khabieh)
Source: United Nations
With Russia supplying weapons to Assad's government, the fighting for major cities like Palmyra and Aleppo continued into 2017. Six years of unabated bombing and fighting caused irreparable damage to Syrian infrastructure and society.
This Nov. 20, 2014 photo shows an area controlled by the Islamic State group, past the Qada Azadi roundabout, foreground, in Kobani, Syria. Amid the wasteland and destroyed buildings, a sense of camaraderie has developed among the town’s defenders who have doggedly fought off militant advances for more than two months. (Jake Simkin/AP)
Source: The Washington Post
On April 7, 2017, Assad's government is believed to have carried out another chemical strike on a town in Idlib province. At least 70 people, including 10 children, died in the attack.
A man carries the body of a dead child, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib (Thomson Reuters)
Source: Business Insider
US President Donald Trump launched cruise missiles at the airfield where Assad's warplanes are believed to have taken off loaded with chemical weapons. It was the first US attack on the Syrian government since the war erupted in 2011.
In this image from video provided by the U.S. Navy, the guided-missile destroyer USS Porter (DDG 78) launches a tomahawk land attack missile in the Mediterranean Sea, Friday, April 7, 2017. (Mass Communication Specialist 3rd Class Ford Williams/U.S. Navy via AP)
Source: Business Insider and Newsweek
As Western countries fight over political influence, the Syrian War continues to ravage, kill and displace Syrian families. Nearly five million people fled the country as refugees and over 400,000 are waiting inside refugee camps.
The ongoing conflict in Syria has created a refugee crisis (REUTERS/Kadir Celikcan)
Source: United Nations
As ISIS becomes less of a threat in the region, groups that have had an unofficial truces have had numerous skirmishes, or have openly started fighting each other. In January 2018, Turkey launched "Operation Olive Branch," a military intervention into Syria's Kurdish-controlled Afrin Region to to replace Kurdish authority with a different faction.
Turkish troops take control of Bursayah hill, which separates the Kurdish-held enclave of Afrin from the Turkey-controlled town of Azaz, Syria, January 28, 2018. (Associated Press)
Source: Al Jazeera
On February 7, 2018, up to 200 "pro-regime forces," reportedly Russian mercenaries, were killed in US airstrikes after they attacked US-backed Kurdish forces and their American advisors across the Euphrates River.
A "pro-regime forces" T-72 tank, possibly manned by Russian citizens moments before being destroyed by a US airstrike, (U.S. Air Forces Central Command Public Affairs)
Source: Business Insider
On February 10, 2018, Israel shot down an Iranian drone that had entered its airspace. The Israelis retaliated by bombing Iranian and Syrian positions in Syria. Syria managed to shoot down an Israeli F-16 over Israeli airspace. The Israeli response was called off after Russian President Vladimir Putin called Prime Minister Benjamin Netanyahu and told him to de-escalate.
Israeli security forces examine the remains of an F-16 Israeli war plane near the Israeli village of Harduf (Thomson Reuters)
Source: Business Insider
While not over, the Syrian Civil War in entering a new phase. ISIS is becoming less of a threat, Assad has, with the help of the Hezbollah, Iran, and the Russians, taken much rebel-held territory. The Kurdish SDF is now the second largest group in the region, but it is not clear if it will integrate with the Syrian government.
A map showing the status of the Syrian Civil War in March 2018. Red represents the Syrian government, yellow the SDF (Kurds), green the numerous rebel groups, black ISIS, and white Tahrir al-Sham. (Wikimedia commons)
The Civil War has also spurred the biggest global refugee crisis since World War II. Nearly half of Syria's pre-war population has been internally displaced or forced to flee their homes for other countries in the Middle East, Europe, and North America.
Refugees and migrants arrive on an overcrowded boat on the Greek island of Lesbos, November 10, 2015. (Thomson Reuters)
On April 8, 2018, Syrian opposition activists and aid groups claimed that a chemical weapons attack on the city of Douma, a rebel held enclave near Damascus, killed dozens of people, including children.
Two children are treated following a suspected chemical weapons attack in the Syrian city of Douma, just 6 miles away from the center of Damascus, April 8, 2018. (Screenshot/The White Helmets)
The response to the attack was intense. Trump called Assad an "animal," and warned that there would be a "big price to pay." Israel, meanwhile, reportedly conducted an airstrike at the T4 air base in Homs province, the same base they had struck almost two months before.
A man is washed following alleged chemical weapons attack, in what is said to be Douma, Syria in this still image from video obtained by Reuters on April 8, 2018. (Helmets/Reuters)