Foreign fighters have fought on all four sides of the Syrian Civil War, as well both sides of the War in Iraq. In addition to Sunni foreign fighters, Shia fighters from several countries have joined pro-government militias in Syria, leftist militants have joined Kurdish forces, and other foreign fighters have joined jihadist organizations and private military contractors recruit globally. Estimates of the total number of foreign Sunnis who have fought for the Syrian rebels over the course of the conflict range from 5,000 to over 10,000, while foreign Shia fighters numbered around 10,000 or less in 2013 rising to between 15,000 and 25,000 in 2017.
Throughout 2014, with the rise of Islamic State, the Al-Nusra Front, and other groups, their numbers drastically increased and they partnered with and absorbed Syrian rebel groups, both jihadist and non-jihadist. By 2015, foreign jihadists outnumbered Syrian jihadists and other rebels in casualty rolls (16,212 anti-government foreign jihadists were killed in 2015 compared to 7,798 Syrian anti-government rebels killed that same year), a trend that carried over into 2016 (13,297 foreign jihadists and 8,170 Syrian rebels), and 2017 (7,494 foreign jihadists and 6,452 Syrian rebels). However, although the numbers of casualties remained high in this phase, arrivals slowed: according to the United States military, foreign fighters coming to Syria and Iraq in 2013-2015 averaged 2,000 fighters per month, but by 2016, this figure had dropped to less than 500 fighters per month and decreasing. By 2018, the proportion of foreign fighters had far decreased (following heavy losses in the bloody battles of 2015-2017 and various interventions by foreign military forces), and Syrian rebels were once again the majority of anti-government casualties (2,746 foreign jihadists killed compared to 5,852 Syrian rebels).
According to the Syrian Observatory for Human Rights, at least 65,726 anti-government foreign fighters (almost entirely jihadists) were killed in Syria up to May 2020, constituting nearly half of the 138,202 anti-government fighters killed by that point. Additionally, 10,045 foreign fighters on the side of the Syrian government were killed by then (1,700 Lebanese Hezbollah and 8,345 others, including 2,000+ militiamen of Liwa Fatemiyoun) and 264 Russian soldiers and mercenaries.
Reasons.
Jihadism.
Many of the foreign fighters in Syria and Iraq were drawn to the jihadist ideology, although experts note that religion is not the only motivation:
From ignorant novices who view the trips as a rite of passage, die-hard militants looking for combat and martyrdom, and individuals who go for humanitarian reasons but get drawn into conflict, individuals become foreign fighters for a range of reasons: boredom; intergenerational tensions; the search for greater meaning in life; perceived adventure; attempts to impress the local community or the opposite sex; a desire for increased credibility; to belong or gain peer acceptance; revenge; or misguided conflict experience expectations.
Foreign fighters were drawn both to the Islamic State and other Islamist fighting groups, such as the Nusra Front, Liwa al-Muhajireen wal-Ansar, and (prior to 2013) Ahrar al-Sham. Jaysh al-Islam rebel leader Zahran Alloush called for foreign fighters to come to Syria, although experts report that the group does not include foreign fighters. On 31 May 2013, Yusuf al-Qaradawi called for a jihad against Syria. It was speculated in the Western media that this could lead to an influx of foreign fighters to the country, although no reports emerged that this transpired.
Shia activism.
Thousands of foreign fighters are in Syria from Iraq, Lebanon, Iran, Pakistan, Afghanistan, and Bahrain with Shia sectarian militias fighting in defence of the Assad government.
Left-wing support for Rojava.
Hundreds of foreign leftists have joined the International Freedom Battalion of the People's Protection Units (YPG) in Rojava, out of a mixture of opposition to the Islamic State and willingness to defend the Rojava Revolution. Foreign volunteers are supposed to follow the YPG's values of democracy, ecology, Jineology, and some of them anti-capitalism.
Left-wing support for Syrian rebels.
Although they are less numerous than leftist foreign fighters joining the YPG, there have also been left-wing foreign fighters alongside Syrian rebels, including the Trotskyist Leon Sedov Brigade founded by an Argentine leftist who fought with the Free Libyan Army.
Right-wing support for Assad.
The European and North American far right is generally supportive of the Assad government in Syria, and far right foreign fighters, e.g. from Greece and Scandinavia, are found in pro-government militias.
Mercenaries and private contractors.
In addition to volunteer foreign fighters, there are several private military companies operating in Iraq and Syria, such as the Wagner Group and the Slavonic Corps.
Passage.
Most fighters travel to Turkey first before slipping across the border with somewhat lesser contingents coming from Lebanon and even fewer from Jordan and Iraq; many of the fighters also use forged passports as they try to escape secret services. Upon entering the country, many of the Islamist fighters were dispersed to the various groups such as Ahrar ash-Sham and the Nusra Front. Languages reportedly spoken in rebel camps include: Chechen, Tajik, Turkish, French, the Saudi Arabic dialect and Urdu (Pakistan or India). In regards to the Free Syrian Army, "The Guardian" reported the recruits to be more secretive. Jihadist internet fora have also been fertile recruiting grounds.
Even in July 2013, it was reported that foreign fighters continued to come to Syria and commit atrocities against both supporters and opponents of the government, as well as clashing with moderate rebel groups. This followed President Bashar al-Assad signing into law a bill that would punish anyone entering the country illegally with jail time and a fine. The fine would be between five million and 10 million Syrian pounds.
Islamic State foreign fighters.
According to figures collected by the "Soufan Group" in 2016, between 27,000 and 31,000 people including women and children who would not normally engage in conflict had traveled to Syria and Iraq to join the Islamic State and other extremist groups fighting in the region.
One reason suggested for the influx of foreigners in the fight is that the Syrian government took no steps to curtail the inflow of foreigners moving into Iraq during the Iraqi insurgency. In the first half of 2012, 700-1,400 fighters were said to have entered Syria. Their numbers continued to increase, however, and by 2013 may have numbered more than 11,000. The Turkish border was how most jihadis entered Syria.
An October 2016 World Bank study found that "ISIL's foreign fighters are surprisingly well-educated." Using the fighters' self-reported educational levels, the study concluded that "69% of recruits reported at least a secondary-level education" of which "a large fraction have gone on to study at university" and also that "only 15% of recruits left school before high school; less than 2% are illiterate." The study also found that foreign fighters are often more educated than their countrymen where those "from Europe and in Central Asia have similar levels of education to their countrymen" while those "from the Middle East, North Africa, and South and East Asia are significantly more educated than what is typical in their home nations." The report notes that its conclusions that terrorism is not driven by poverty and low levels of education does not conform with previous research. However, the report did find a strong correlation "between a country's male unemployment rate and the propensity of the country to supply foreign fighters" leading the report to recommend that governments pursue a policy of lowering the unemployment rate among the educated as a counter-terrorism strategy.
In December 2018, Kurdish authorities held 550 foreign women about 1200 in captivity. A large part of the children were born in Syrian territory controlled by the Islamic State. Many of the women still shared the Islamic State ideology and lacked passports and therefore Kurdish authorities were reluctant to release them. While initially the women and children were kept along civilian Syrian refugees, this proved untenable as hard-liners among the women caused problems when they ganged up and assaulted women who took off the Islamic burqa. They also prevented other women and children from listening to music provided by their captors. In October 2019, hundreds of inmates with suspected links to the Islamic State reportedly fled a displacement camp based in north-east Syria, following the Turkish offensive in the region. This raised concerns of resurgence of the Islamic State amid conflict.
Origins of foreign fighters.
Fighters include those from the Gulf Arab States, the Levant, the Maghreb, Turkey, Egypt, Sudan, the Muslim regions of Eastern Africa, the Muslim regions of the Balkans (especially Bosnia and Herzegovina, Kosovo and Albania), the Muslim regions of Russia (especially the North Caucasus region), the Muslim regions of Southeast Asia, and many Western countries. Some jihadist groups are dominated by a single nationality, as is the case with the Caucasus Emirate (Chechens) and the Turkistan Islamic Party (Uyghurs), or the pro-government Afghan Shia Liwa Fatemiyoun.
A 7 December 2015 report by the "Soufan Group" gave estimates for the number of foreign fighters in Syria and Iraq by their country and region of origin based on information dated between 2014 and 2015. The study, which only included foreign fighters with the Islamic State, the Nusra Front and other Sunni jihadist factions, listed the countries with the largest number of foreign fighters were Tunisia (6000), Saudi Arabia (2500), Russia (2400), Turkey (2100), Jordan (2000+) while the number of fighters by region was reported to be: the Middle East (8240), the Maghreb (8000), Western Europe (5000), former Soviet Republics (4700), Southeast Asia (900), the Balkans (875), and North America (289). Of Western Europe's estimated 5000 total fighters, almost 3700 fighters were produced by just four Western European countries: France (1700), Germany (760), the United Kingdom (760), and Belgium (470). Between 2014 and 2015, the report estimated a nearly 300% increase in the number of fighters originating from Russia and Central Asia whereas the total number of fighters traveling to Syria and Iraq had become "relatively flat." The report mentioned that the flow of foreign fighters "is neither uniform by region nor by country," with some countries having distinguishable "Hotbeds of recruitment" with some hotbeds, such as the Lisleby district of Norway's Fredrikstad which is populated by only 6000 people, being small and relatively new while other cities and regions, such as Tunisia's Bizerte and Ben Gardane, Libya's Derna, Georgia's Pankisi Gorge, and Brussel's Molenbeek, "are well-established incubators and radiators of extremist behavior." The Soufan Group reported on 15 October 2016 that there has been "a significant increase in the number of foreign fighters travelling to Syria" since 2014. The U.S. State Department reported on 2 June 2016 that their "intelligence community" estimates that possibly "in excess of 40,000 total foreign fighters have gone to the conflict [in Syria] and from over 100 countries".
The phenomenon causes concerns in the home countries of the foreign fighters. The phenomenon is not new, but the size and variety of origins in this case were unusual.
Arab world.
In 2012, it was reported that most recruits to Syria are Arabs (Lebanese, Iraqis, Jordanians, Palestinians, Kuwaitis, Tunisians, Libyans, Algerians, Egyptians, Saudis, Sudanese and Yemenis). The largest contingents of about 500-900 fighters came from Syria's neighbors: Lebanese, Iraqis, Palestinians and Jordanians, many of whom fought U.S. forces in Iraq. The second-largest contingent was from Arab countries in North Africa: around 75-300 fighters from Libya, Tunisia, and Algeria. Al Qaeda leader Ayman al-Zawahiri called for a jihad in Syria with the main target of message said to be Lebanon, Jordan, Turkey and Iraq.
Gulf states.
In 2013, Bahraini Sunni sheikh Adel al-Hamad said that his son, Abdulrahman, was killed while fighting in Syria and that he had "hoped to fall as a martyr." He added: "He visited Syria once, then he returned to Bahrain where he prepared his fighting gear and returned to Syria." In response, Interior Minister Rashid bin Abdullah al-Khalifa said that support should be given from the international community and that individuals should not be indoctrinated and radicalised. It follows calls from mosques to join the "jihad" in Syria. There are also Saudi fighters. In 2013, "USA Today" reported that over 1,200 death row inmates were sent from Saudi Arabia to fight against the Syrian government.
Bahraini Shia youth traveled to receive Iranian training in camps and battlefronts in Iran, Lebanon, Iraq, and Syria, and there have been reports that a Bahraini Shia militia, Saraya Al Mukhtar (The Chosen Brigades), was fighting in Syria on the pro-government side in 2015.
Lebanon.
Mostly Lebanese fighters in Syria tend to have their own groups and militias. Thousands of Lebanese fight on the pro-government side. The most