Syria's long civil war has reclaimed global attention after insurgents took control of Damascus over the weekend and toppled the 50-year Assad regime.

On Tuesday, Syria's new interim leader announced he was taking charge of the country as caretaker prime minister with the backing of the former rebels who toppled President Bashar al-Assad three days ago.

In a brief address on state television, Mohammed al-Bashir, a figure little known across most of Syria who previously ran an administration in a small pocket of the northwest controlled by rebels, said he would lead the interim authority until March 1.

The stunning advance by rebel forces over the last two weeks came as several key players in the conflict have been distracted or weakened, triggering the heaviest clashes since a 2020 ceasefire brought relative calm to the country's north.

Here's a look at the key players.

5 foreign powers in Syria

Syria's civil war started in 2011 after an uprising against Assad's rule. Five foreign powers have a military presence in the country: the United States, Russia, Iran, Turkey and Israel. Forces opposed to Assad, along with U.S.-backed fighters, had controlled more than a third of the country.

Turkey has deployed troops across northwestern Syria — territory held by Syrian rebel groups that rose up against Assad in 2011. Turkey, which firmly supported the 2011 uprising, backs some of these rebel groups.

Iran deployed its Revolutionary Guards to Syria as early as 2012 to help Assad. Lebanon's Hezbollah, which is backed by Iran, played a big part. For Iran, Assad is a crucial ally, part of its "Axis of Resistance" to Israel and U.S. influence in the Middle East.

The U.S. military intervention in Syria began in 2014 with airstrikes against the Islamic State jihadist group that had declared its rule over a third of Syria and Iraq. U.S. forces remain in Syria and continue to support the Syrian Democratic Forces (SDF).

Russia intervened militarily on Assad's side in 2015, in its biggest foray in the Middle East since the Soviet Union's collapse. Operating from an airbase in Latakia province, Russian air power decisively tilted the conflict Assad's way.

Israel holds the Golan Heights, which it seized in its 1967 war with its Arab neighbours. On Monday, Israeli forces seized a buffer zone in the Golan Heights established by a 1974 ceasefire agreement with Syria. Israel has denied reports that its forces had advanced beyond the buffer zone into the countryside southwest of Damascus.

The presence of Iranian and Iran-backed forces in Syria has been a big point of concern for Israel, prompting it to carry out frequent airstrikes in Syria.

Syrian pro-government forces. Backed by Russia, Iran

Syrian government troops have long controlled a large part of the country, thanks to allied forces dispatched by Russia and Iran.

Until this weekend, Assad's forces controlled most of the major population centres, including the capital Damascus and cities in Syria's centre, south and east. The Syrian government's capture of Aleppo in late 2016 was a turning point in the conflict — and their loss of the city in recent days is a major setback.

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After decades in power, the Assad regime has fallen to Syrian rebel groups led by Hayat Tahrir al-Sham. Andrew Chang breaks down the two weeks of intense fighting that led to this seismic breakthrough for rebel forces. Images supplied by Getty Images, Canadian Press and Reuters Connect. Additional credits: 0:05: BBC News/YouTube, 0:09: PBS NewsHour/YouTube, 0:13: Social media via Reuters, 0:14: Social media via Reuters, 1:52: FRANCE 24 English/YouTube, 1:56: FRANCE 24 English/YouTube, 1:57: ABC News (Australia)/YouTube

Iran's military advisers and proxy fighters have played a critical role in shoring up Assad's forces throughout the war. But Lebanon's Hezbollah militant group, which is backed by Iran, has been weakened in its recent war with Israel and Iran has been distracted by the conflict. Last week, Iranian-backed Iraqi militias deployed to Syria to back the government's counteroffensive.

Russia's military has supported Assad from the Mediterranean coast, where it maintains its only naval base outside the former Soviet Union, and at the Hmeimim airbase in Latakia province, which is home to hundreds of Russian troops. But much of its attention and resources have been focused on its war in Ukraine.

The Kremlin said on Monday that Russia has granted political asylum to Assad.

Insurgent groups. Backed mainly by Turkey

Anti-government forces are led by the insurgent Hayat Tahrir al-Sham (HTS), which long served as al-Qaeda's branch in Syria and is considered a terrorist group by the United Nations as well as countries including the U.S. and Canada.

Public Safety Canada noted that Jabhat Fateh al-Sham (JFS), which in 2017 merged under HTS, has claimed responsibility for hundreds of attacks, including ambushes, kidnappings, assassinations, suicide bombings and improvised explosive devices.

HTS had controlled much of northwest Syria and in 2017 set up a "salvation government" to run day-to-day affairs in the region. In recent years, its leader Abu Mohammed al-Golani has sought to remake the group's image, cutting ties with al-Qaeda, ditching hard-line officials and vowing to embrace pluralism and religious tolerance.

WATCH | Who is Abu Mohammed al-Golani? 

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Other insurgent groups include Noureddine el-Zinki, which was formerly backed by the U.S., before it joined the HTS-led alliance.

A Turkish-backed coalition of groups known as the Syrian National Army has attacked areas including the northern town of Tel Rifaat, controlled by the U.S.-backed and Kurdish-led Syrian Democratic Forces.

Chinese fighters from the Turkistan Islamic Party and Chechen fighters from the former Soviet Union have taken part in the battles in the country's northwest, according to Syrian opposition activists.

Turkey, which controls parts of northern Syria, will not say how many troops it has in the country.

Syrian Democratic Forces. Backed by the U.S.

The Kurdish-led Syrian Democratic Forces, a U.S.-backed coalition of groups, control large parts of eastern Syria.

The SDF has battled the Islamic State group, capturing the last sliver of land held by the extremists in eastern Syria. About 900 American troops are stationed in Syria's east to guard against a resurgence by the extremist group.

On Sunday, the U.S. launched one of its larger, more expansive assaults against IS camps and operatives in the desert, taking advantage of the Assad government's downfall. So far, U.S. officials say they do not plan an increase in American forces in Syria but are focused on making sure those already there are safe.

Turkey considers the principal Kurdish faction of the SDF to be linked to the banned Kurdistan Workers' Party, or PKK, which it and its allies regard as a terrorist group.