Northeast Syria is home to a number of forces with different interests, with the Kurdish militia controlling the most territories.

Russian soldiers on October 15 began patrolling the buffer zone between Syrian and Turkish government troops on the outskirts of Manbij city to prevent the two sides from fighting. The city is now under the control of the Russian-backed Syrian government army, Russian soldiers are also coordinating operations with the nearby Turkish army.

The move comes after the United States withdrew its forces from northern Syria. The presence of Russian troops can prevent major conflicts between Ankara and Damascus, but it is difficult to control the long-running territorial rivalry in the area, experts say.

Kurdish People's Protection Units (YPG) are the main targets of Turkey's Spring Peace campaign. This is the core of the US-backed Syrian Democratic Forces (SDF), but still pursues its own goals such as building an independent Kurdish nation.

YPG is considered by Turkey to be a branch of the Kurdish Workers' Party (PKK). In the past, Ankara has repeatedly threatened to launch unilateral military operations into Syrian territory to drive Kurdish militia out of the border.

Since 2012, the YPG has begun to increase its presence in northeastern Syria after supporting President Bashar al-Assad's government to repel the rebel forces. The YPG expands its territory through control of villages and towns from Syrian rebels, as well as the acquisition of land from the self-proclaimed Islamic State (IS) organization.

Before the Spring of Peace campaign was launched by Turkey, the YPG was the most dominant force in northern Syria. "Turkey's war will not be easy. They dominate the weaponry, but face very disciplined YPG forces and have been trained through years of urban warfare with ISIS," pen Khaled Yacoub. Oweis of National commented.

The Syrian Democratic Forces (SDF), founded by Washington to recruit northern Syrian tribes for the fight against IS, are composed of YPG and Arab militants.

The US has trained thousands of SDF soldiers in tactics, reconnaissance and first aid. Reconnaissance teams are trained to determine the location of the IS rebels and then transmit information to the command center of the US-led coalition, from which to plan air strikes.

"Over the past two years, the coordination has become extremely profound. The level of trust in each other is also very high, because this cooperation has brought tremendous results," Mutlu Civiroglu, an analyst at for Kurds, explained. "SDF and the US coalition complement each other. US forces are not present on the ground, and SDF has no air support, so they need each other."

Even after IS lost most of the land, the United States trained SDF anti-terrorist units to raid Islamic militants' hideouts and provide them with the necessary intelligence. SDF also often escorts American convoys through several towns in Syria, or protects the outside for places with Americans inside.

The Syrian National Army (SNA) is a rebel group playing an important role in Turkey's Spring of Peace campaign. It is Ankara's proxy force with the Free Syrian Army (FSA) and other rebel groups pushed back to Idlib province and northern Aleppo after Russia's military intervention in Syria in 2015.

SNA plays an important role in Turkey's strategy as it frequently operates in the area established by Ankara west of the Euphrates River. SNA's Twitter account on October 9 confirmed it was cooperating with the Turkish army in the campaign in northeastern Syria.

The Kurdish National Council (KNC) is an alliance of Kurdish political parties supported by Masoud Barzani, a Kurdish commander living in Iraq. Unlike the YPG, many KNC members have been incarcerated after participating in the movement against President Assad. Barzani has formed a militia group in Syria trained and coordinated by the Kurdish forces in Iraq (Peshmerga) for the KNC.

Situation of factions controlling Syrian territory on October 13. Graphics: RFE.

Arab tribes in northeastern Syria have historical ties with the factions in Iraq and Saudi Arabia, but support the Syrian government. In areas outside the government's control, these tribes primarily supported the FSA, al-Qaeda and IS, before becoming members of the regional management council established by the YPG.

Another force is also taking advantage of the confusion in northeast Syria to rise as IS militants. Although US-backed forces declared a complete defeat of the IS after the battle at Baghouz in March, militants remained underground and occasionally launched attacks against the YPG.

As the Kurdish militia engrossed in dealing with the Turkish army in the north, they would have to leave a lot of gaps in the rear, creating favorable conditions for the IS to continue its rise.