As President Donald Trump ordered the precision strikes on chemical weapons targets in Syria Friday night, the retaliatory move shined a spotlight on the players involved in the conflict -- from Syria and the United States, to Russia, Iran and Israel.
The U.S. president addressed the nation shortly after 9 p.m. ET -- and wasted little time calling out two of Syria's strongest allies.
"I also have a message tonight for the two governments most responsible for supporting equipment and financing the criminal Assad regime. To Iran and to Russia, what kind of a nation wants to be associated with the mass murder of innocent men, women and children?" Trump said.
"The nations of the world can be judged by the friends they keep," the president added. "No nation can succeed in the long run by promoting rogue states, brutal tyrants and murderous dictators."
Tensions are flaring between Syria and the international community in the wake of a suspected chemical weapons attack last weekend that left at least 40 dead, according to activists and medics.
But the recent incident is just the latest in a conflict that is in its eighth year and has led to around 350,000 deaths, according to the Syrian Observatory for Human Rights, a British-based watchdog. The war has grown to encompass many players, from the Syrian regime and opposition to Russia, the United States, Iran, Israel and various terrorist groups.
Here is a breakdown of all the significant players in the conflict, what they stand to gain and lose, and how they’ve impacted the trajectory of this long and brutal war.
Assad and his major ally, Russia
The conflict in Syria began as a popular uprising against totalitarian President Bashar al-Assad. In the early years of the conflict, essentially a civil war between the government and the rebellion, Assad’s forces sustained many losses, and were once thought to be on the edge of collapse.
However, the Assad government’s efforts were bolstered by the assistance of artillery, troops and air support from their longtime ally Russia. Assad's government has always had air force superiority over the rebels, often dropping barrel bombs on rebel enclaves. But Russia has poured billions of dollars into propping up the Assad government and enabling it to beat back the rebels and Islamic militant groups.
Russia’s interest in Syria is geopolitical. Syria serves as an access point to the Mediterranean Sea, an important port for Russia. The country is also a hub for Russia in the Middle East.
"In 2013, President Putin and his government promised the world that they would guarantee the elimination of Syria's chemical weapons," Trump said in his Friday night address. "Assad's recent attack, and today's response, are the direct result of Russia's failure to keep that promise.
"Russia must decide if it will continue down this dark path or if it will join with civilized nations as a force for stability and peace," he added. "Hopefully one day we'll get along with Russia, and maybe even Iran, but maybe not."
Most of Iran practices Shi’ite Islam, and Assad belongs to the Alawite sect of Shi’ite Islam (most Syrians are Sunni Muslims). Because of this religious tie, Iran has great interest in the well-being of Assad’s government.
Iran, like Russia, is spending billions in Syria. The United Nations estimated that at one point, Iran was spending $6 billion per year there. The head of Iran’s Martyrs Foundation has acknowledged that more than 2,000 Iranian soldiers have died in Syria, including generals from its Islamic Revolutionary Guard Corps.
On top of religious motivations, Iran for years used Syria as a conduit to send arms and funds to Hezbollah, the Lebanese militant group responsible for the 1983 Beirut barracks bombings that killed 241 American service members.
When the path through Syria was threatened by the civil war, Hezbollah and Iran both started supporting Assad’s regime in the fight. Today, Hezbollah has thousands of fighters on the ground and have sustained significant fatalities.
Where Iran has interest, so will Israel, as Iran’s major regional rival.
Israel perceives Iran as a major long-term threat, and as Russia’s involvement stabilized the Assad regime in 2015, Iran and Hezbollah’s influence in Syria increased as well. Israel decided to protect their own interests by beginning airstrikes deep into Syrian territory in September 2017.
After the chemical attack in Douma on April 7, Israel was the first to respond, conducting an airstrike on the T-4 airfield in Syria, proving the Israelis are willing to act unilaterally in Syria.
ISIS took advantage of the power vacuum created by the civil war to rise to prominence in 2014, gaining significant territory and establishing their self-described “caliphate,” centered in Raqqa.
But ISIS’s influence has diminished significantly in the face of both the Global Coalition to Counter ISIS, headed by the United States, and the Assad alliance. The brutal terror group holds a fraction of the territory they gained in 2014.
Terror group al-Qaeda has also played a role in Syria, albeit a smaller one. ISIS began as an al-Qaeda affiliate, but the two groups split in early 2013 due to differing ideology. In the wake of the division, al-Nusra Front emerged as al-Qaeda’s offshoot and the U.S. targeted them with airstrikes on a handful of occasions.
Eventually, al-Nusra Front claimed to have severed ties with al-Qaeda as well and changed its name to Tahrir al-Sham, although many analysts believe it is still al-Qaeda’s affiliate on the ground. The U.S. government added the group to its list of terrorist organizations that are sanctioned, but at times moderate opposition forces fight alongside it.
Other opposition forces
Another key force on the battlefield is Ahrar al-Sham, an umbrella group of hard-line militants that want to replace Assad with an Islamic government. Despite some overlap in ideology, they also fight against ISIS and, at times, Tahrir al-Sham. Along with the FSA and some other Islamic groups, these are the principal forces on the front lines that Assad battles.
Many of these groups have been secretly supported and armed by Saudi Arabia and other Arab countries like Jordan and the Gulf states.
The Assad regime has been quick to label anyone in the opposition against it a "terrorist," accusing those groups' Western and Arab allies of supporting terrorism. Russia considers Ahrar al-Sham to be part of the "moderate opposition" included in its cease-fire negotiations with Iran and Turkey, but the group declined to attend those talks.
Turkey and the Kurds
Last, but certainly not least in battlefield capability or influence is Turkey, Syria’s neighbor to the north. Turkey remains a fickle, but critical, American ally.
Turkey launched a ground campaign in northern Syria last August, sending troops, tanks and planes across the border to push back ISIS. That operation, known as Euphrates Shield, has concluded, liberating key cities like Jarabulus and Manbij. But Turkey remains heavily involved in the conflict, especially through its support for opposition groups.
The U.S. angered major ally Turkey in May 2017 when President Donald Trump approved a military plan to arm the Kurdish YPG militia as part of the effort to retake Raqqa.
The Kurds are an ethnic group who joined the fight against ISIS. As ISIS was defeated, the Kurds retained control of certain regions, setting up aspirational local governments, especially in the northern towns Afrin and Manbij.
But Turkey views the YPG as an arm of the Kurdistan Workers’ Party (PKK), which is considered by the U.S. to be a terrorist group and has fought a decades-long insurgency in Turkey.
In an effort to remove the Kurds from some of the border areas Syria shares with Turkey, Turkish forces invaded Syria in January, putting two U.S. allies and partners in the fight against ISIS against one another.
Russia has said it will not interfere in the conflict between Turkey and the Kurds.