While the Islamic State (IS) has swept away the armies that have stood before it, a little-known group fighting its own war against the extremist group has done remarkably well.
The People's Protection Units (Yekîneyên Parastina Gel: YPG) are the defence force of the Democratic Administration of Rojava: the de facto autonomous Kurdish region that has been formed in northeast Syria since the outbreak of that country's conflict in 2011. Currently engaged in combat against the IS on five front lines across northern Syria, the YPG is perhaps one of the only forces that knows how to take on the extremists at their own game.
Relying on speed, stealth, and surprise, it is the archetypal guerrilla army, able to deploy quickly to front lines and concentrate its forces before quickly redirecting the axis of its attack to outflank and ambush its enemy. The key to its success is autonomy. Although operating under an overarching tactical rubric, YPG brigades are inculcated with a high degree of freedom and can adapt to the changing battlefield.
The IS has fared well against more static forces using Soviet-based doctrines, which have proven wholly incapable of countering its highly mobile forces. Both the IS and the YPG, however, have emerged from the ashes of the Syrian conflict and have adapted their fighting styles to the territory in which they operate.
The YPG relies heavily on snipers, backed by mobile support weaponry (mainly 12.7 mm Russian-issue heavy machine guns) that carve up the battlefield and suppress enemy fire. It also uses roadside bombs to limit enemy movement and prevent outflanking manoeuvres, particularly at night.
While Iraqi Kurdish forces (known collectively as the peshmerga) are receiving military assistance from countries including France, Germany, the United Kingdom and the United States, the Syrian Kurds have received little such help. Accusations that they remain close to the regime of Syrian President Bashar al-Assad, whose forces withdrew from Kurdish territory in 2012, and that they are closely linked to the Kurdistan Workers' Party (PKK), which is fighting for Kurdish independence from Turkey, make them an unpalatable choice.
Turkey in particular believes the YPG to be a tool of Damascus, while those who believe the Rojava government's aims run against the goals of the Syrian opposition often accuse the Syrian Kurdish region of being a haven for Iranian influence.
The Syrian Kurds are essentially operating in an isolated canton facing the IS to the south and a deeply suspicious and hostile Turkey to the north, while Iraq's Kurdistan Regional Government (KRG) cannot decide whether they are friend or foe.
As a result, YPG units are poorly equipped. None observed by IHS Jane's during a recent visit to Syrian Kurdistan used body armour or helmets. Weapons and ammunition are purchased on the black market.
The Syrian Kurds have also suffered significant casualties in the constant attacks and counterattacks along the 900 km front. For example, the battle of Jazza'a (a strategic town on the Syria-Iraq border that protects the humanitarian corridor) lasted for nine days from 19 August and cost both sides tens of casualties.
Yet the YPG's lines have yet to break when attacked by better-equipped IS forces. The YPG has even managed to expand into Iraq, largely thanks to the retreat of the KRG's peshmerga from around Mount Sinjar following the IS advance in early August. The persecuted Yazidi minority fleeing the conflict were protected by YPG units before making their way north via the humanitarian corridor running through northeast Syria into Turkey.
Eager to avenge IS atrocities, many Yazidis have asked the YPG for weapons and training. The YPG has so far trained more than 1,000 in one-week military courses and sent them back to Sinjar, where they operate as local defence units under YPG and PKK supervision. The result is that the YPG now occupies areas in Iraq previously controlled by the peshmerga.
YPG officials deny having permanent intentions on Iraqi territory, but it is unclear what the future holds. Even if the YPG withdraws from the Sinjar area, the Yazidi units left behind appear loyal to the YPG, not the peshmerga. For their part, the Iraqi Kurds have insisted there can be no discussion on this matter and that the YPG presence is a violation of sovereignty.
For now the YPG and peshmerga appear to be putting their differences aside. However, serious problems could emerge once the IS threat recedes. Indeed, both Iraqi and Syrian Kurdish officials told IHS Jane's they will try to resolve the issue amicably, while each casting the other side as the instigator.
The future for the YPG holds more conflict. The IS is unlikely to cease its attacks on the Kurds for the time being, given that they control strategic border crossings and block the road from its capital in Syria's Al-Raqqah across to the city of Aleppo. Syria's Kurds appear capable of holding out, but they know that more martyrs (who are glorified in their culture) will fall before the IS is permanently beaten back.