Free Syrian Army
Free Syrian Army fighters pose after capturing the Military Infantry School in Aleppo Dec. 16, 2012. Reuters

It has been nearly two years since a group of schoolchildren in Syria scrawled revolutionary graffiti on the side of a building in the southern city of Daraa. Their subsequent arrest and mistreatment in prison turned widespread dissent, which was simmering at the time, up to a full boil. Early peaceful protests were met with violence, demonstrators eventually responded in kind, and a national militant rebellion began to take shape.

Today, 23 months later, Syria is in the middle of one of the world's bloodiest crises in recent memory.

The U.N. estimates that more than 70,000 men, women and children have lost their lives since the conflict began in earnest in March of 2011. The well-equipped forces of the regime are maintaining key strongholds and raining missiles into rebel-held territories, but the opposition fighters -- whose arms are comparatively light -- refuse to back down.

Political freedom and human rights are still at the root of the rebellion, but things have changed since the uprising began. And with each passing month, one key question becomes more and more difficult to answer: Who, exactly, are the people fighting to oust the regime of Syrian President Bashar al-Assad?

The forces clashing with Assad’s troops are as diverse as they are determined, but fragmentation among their ranks is an enormously sensitive subject. Not only does it threaten future stability in Syria; it also risks validating outsiders’ concerns about the uprising.

Since the beginning of the rebellion, Assad himself has justified regime crackdowns by casting the militants as foreign-backed terrorists. His aim was to shift focus away from his authoritarian government’s transgressions, which include human rights violations, suppression of political dissent, arbitrary expansions of executive power and rampant nepotism that bled into the private sphere.

The more foreign fighters and Islamist extremists take up arms, the easier it becomes for Assad to defend his crimes.

In addition, concerns about who's actually fighting in the uprising have contributed to preventing foreign assistance. Major powers, including the United States, have not sent weapons to the rebels due to concerns that the arms would fall into the hands of extremist actors.

Those concerns are not unfounded. What began as a secular uprising has morphed into a complicated conflict that exacerbates sectarian differences and attracts international militants. The network of fighters can be difficult to keep track of; opposition groups on the ground number in the hundreds, and the overlaps between various brigades, activist groups and umbrella organizations are myriad.

Outlined here are just a few of the key players involved.

The Politicians

The Syrian rebellion is far from cohesive -- it lacks a strong chain of command, and ongoing turmoil makes it difficult for disparate fighting groups to plan for a political future after the fall of the regime.

To fill that gap, Syrians abroad -- many of them self-exiled dissidents who left during the brutal 1971-2000 reign of Hafez al-Assad, Bashar’s father -- are working to lead the opposition from outside Syria’s borders.

The Syrian National Coalition for Opposition and Revolutionary Forces is currently the preeminent political bloc. Its role as a legitimate representative of the Syrian people has been recognized by various nations, including Saudi Arabia, Turkey, France, Qatar, the United Kingdom, Egypt, the United States and Germany.

The coalition was founded in November of 2012 in Doha, Qatar, and is now based in Cairo, Egypt. It replaced a similar group called the Syrian National Council, or SNC, which had attempted to represent the uprising since in 2011 but was rendered ineffective by infighting and a lack of coordination with Syrian militants on the ground.

Today, members of the still-extant SNC hold 22 of 60 seats in the National Coalition.

“The leader of the National Coalition, Moaz al-Khatib, is a Muslim cleric, but he has largely stood for pluralism and democracy; he is not an Islamist,” Dominic Kalms, an analyst with the Jamestown Foundation specializing in the Middle East and Syria, said. “But the SNC’s 22 seats are made up mostly of Muslim Brotherhood members, and that has created a schism between Islamist and secular members.”

That schism, which mirrors divisions between Syrian rebel forces, has compromised the coalition’s ability to lead effectively. The organization has also been criticized for its perceived distance from militias on the ground, just as the SNC was. But it has made use of Syrian-based groups, including Local Coordination Committees and the Supreme Council of the Syrian Revolution, to build up those connections.

There is another political group on the sidelines called the National Coordination Committee, a left-leaning organization with Kurdish roots. But the committee, which is based in Damascus, is unpopular with most rebel groups since it has a more moderate stance regarding the regime.

“The National Coordination Committee has not demanded necessarily that Assad be extricated from the country,” Kalms said. “They want to end the conflict, but they haven’t explicitly said they want Assad to go. And they reject foreign intervention, which the National Coalition absolutely wants.”

The Revolutionaries

The Free Syrian Army, or FSA, is an umbrella term used to describe most of the forces fighting to topple Assad.

The group has secular and political roots; its stated goal is simply to dismantle the regime. But a clear strain of sectarianism has crept into the movement over the past 23 months, and religion has played a major role; the Syrian rebels are almost entirely Sunni Muslims, while the regime is dominated by Alawites, an offshoot of Shia Islam.

The Syrian National Council has taken steps to align itself more closely with the FSA, but that has been an uphill battle. Some brigades operate within a network linking local battalions to regional military councils and ultimately to FSA leadership, which has command centers in both Syria and Turkey. But tens of thousands opposition fighters operate outside that chain of command and are instead organized according to local affiliations and family ties. Many openly disapprove of FSA and Syrian National Coalition leadership abroad.

While the FSA is nominally secular, the importance of Islamism varies from one battalion to the next.

Toward the secular end of that spectrum are groups like the Khalid bin Walid Brigade, a fighting force based in the Rastan district near the city of Homs. The well-respected unit acts as a security force for opposition supporters and counts among its ranks hundreds of Syrian military defectors.

Then there are Islamist-leaning FSA groups that operate with a higher degree of independence. These include Liwa al-Tawhid, which is thousands of fighters strong and based near the northern town of Aleppo. Though this unit does not explicitly call for an Islamic state, it does employ Sunni rhetoric and cooperate with more extremist groups.

In between are units like the Farouq Brigade, a powerful fighting force that got its start in Homs but has been reportedly engaged in combat as far south as Daraa. Islamist fighters count themselves as members, but leaders of the unit have disparaged jihadist groups operating in the region and pointed to religious diversity in their own ranks.

Defenders Of The Faith

Some Islamist rebel groups do not align themselves with the FSA, though they may work alongside secular battalions as necessary. Many of these religiously conservative brigades operate under the banner of larger umbrella groups, according to Aaron Zelin, an expert on jihadism with the Washington Institute for Near East Policy.

“You have the Syrian Liberation Front, which is a conglomeration of about 20 rebel units. They’re mainly ideologically affiliated with the Muslim Brotherhood,” Zelin said.

“Then you have the Syrian Islamic Front, which is an umbrella organization of about 10 rebel units. They’re Salafist, and they include locally based jihadists.”

The Syrian Islamic Front is the more extremist of these two groups. It includes a brigade called Ahrar al-Sham, which is one of the largest rebel forces in Syria, especially in the northwest.

Ahrar al-Sham leaders use Islamist rhetoric and have called for the establishment of Shariah law in Syria -- though for PR purposes, they take care to walk a fine line between overt jihadism and Syrian nationalism. They have worked with secular fighters but seem keen to maintain their independence from more extremist groups abroad as well as FSA leadership.

Groups operating under the banner of the more moderate Syrian Liberation Front are generally Islamist, but what unites them is the simple goal of unseating Assad. The front shares significant overlap with self-identified FSA fighters.

The Global Jihadists

The most shadowy group operating in Syria today is Jabhat al-Nusra, which has been identified as a terrorist organization by the United States.

“Jabhat al-Nusra is a misnomer. Who they really are is al Qaeda in Syria,” Kalms said.

The group’s roots can be traced back to Iraq, where an organization called al Qaeda in Iraq, or AQI, fought against Western forces following the 2003 invasion. The group is still active there today, targeting mostly Shia communities and confounding government attempts to achieve stability.

“During the invasion of Iraq, Syria was one of the largest transition points for foreign forces coming to fight U.S. forces,” Kalms said. “Now it’s the reverse. You have foreign fighters using Iraq as a transit hub into Syria, not only for fighters but for small arms and explosives. So al-Nusra has been enormously successful.”

Jabhat al-Nusra was founded in 2012. Its militants are notorious for their secrecy and their methods of fighting; by most accounts, they were the first to introduce suicide bombing into the Syrian conflict.

“It’s believed that AQI helped to create Jabhat al Nusra,” Zelin said. “But we don’t know exactly how much command they have over it, since most of the members are Syrian, not Iraqi. But it should be noted that a lot of Syrians in these groups fought in Iraq during the war.”

Neither Jabhat al-Nusra nor al Qaeda has acknowledged affiliation with the other, but evidence strongly suggests a link. Their videos and statements are shared via the same media outlets, there are similarities between their combat methodology, and both claim to be fighting for a jihadist vision that is global in scope.

The Foreign Fighters

Though original FSA fighters might be loath to admit it, foreign militants have played a major role in the Syrian conflict of late. They are most prevalent in Islamist battalions like Jabhat al-Nusra and Ahrar al-Sham, though both groups say Syrians form the majority of their membership.

It is important to note that not all foreign militants have Islamist aims; many have filed into Syria for political reasons, inspired perhaps by successful Arab Spring uprisings in other countries. These fighters bring valuable combat experience. They also bring international connections, helping them to establish supply lines for arms and aid and making them indispensable to the opposition movement.

The exact number of foreign fighters is impossible to pin down, Zelin said. “But based on my own record-keeping, I estimate that between 2,000 and 4,500 fighters have traveled to Syria. In terms of nationalities, toward the top of the list are probably Saudis, Jordanians, Lebanese, Iraqis, Libyans and Tunisians.”

Some foreigners come in with the express purpose of leading Syrian fighters -- like Mahdi al-Harati, an Irish-Libyan fighter who was instrumental in the ouster of Moammar Gadhafi in 2011. His Syrian militant unit, called the Umma Brigade, is known as one of the most organized, well-supplied rebel forces in the country.

But some foreign fighters do bring dangerous elements of terrorism into the mix, as Jabhat al-Nusra shows. The turmoil in Syria has made it increasingly attractive to global jihadists whose presence will endanger the country once it comes time to establish a new political system.

The Endgame

If and when the Assad regime finally crumbles, it will be up to all of these disparate groups to find a way forward. That will be a monumental challenge, especially since Syria has so many internal divisions to contend with.

“One of the most obvious problems is that Syria is a very sectarian country; there are Alawites, Ismailis, Christians, Druze, Sunnis, Shia,” Kalms said. “You only exacerbate these sectarian differences when you have this kind of conflict.”

When the uprising ends, al Qaeda-linked groups will have a stronghold in Syria -- something they were never able to achieve under the secularist regime of the Assad family. Militant groups may resist giving up control of localities they have policed for two years. The National Coalition will undoubtedly meet resistance when it swoops in from Cairo to set up shop in Damascus.

But before all that comes the biggest challenge of all: bringing the Syrian conflict to a conclusion. Nearly two years have passed since this crisis erupted, and the clashes continue to grind on. Hundreds of thousands of people have been displaced. For nonmilitant civilians in several areas, basic needs like food, shelter, electricity and health care are not being met. More blood is spilled with every passing day.

Western diplomats say the reign of Assad will have to end in order to stop this carnage -- and, on that point, at least, the rebel groups are also in agreement.