Over the past years, US troops have supported Kurdish fighters as they battled radical "Islamic State" (IS) militants to take back control of large areas of northern Syria. In what was seen as a surprising turnaround, US President Donald Trump announced in early October that he was withdrawing US troops from the region's border with Turkey. This pullback left a vacuum for others to act and react.

Trump's troop withdrawal was a de-facto go-ahead for Turkey to launch an offensive into northeast Syria. The region is home to a largely autonomous Kurdish population and Kurdish militants known as the YPG, who are tied to an outlawed Kurdish party in Turkey. Turkey, who has faced a Kurdish insurgency, sees the Syrian Kurds as a threat to its security, hence the military action.

The YPG was one of the US' main allies in the fight to drive out IS from north Syria, but since October it has been fighting the Turkish forces that crossed into Syria. The YPG lacks strong air capabilities and defenses, putting it at a decided disadvantage in comparison to the Turkish army.

The YPG is the largest component of the Syrian Democratic Forces (SDF), which also includes Arab and Christian militias. The SDF, which fought IS, controls northeastern Syria and feels betrayed by the US pullback. It is now fighting Turkish troops and their allies. It has warned that the Turkish offensive could distract from making sure IS fighters do not renew their strength in Syria.

The relationship between Syrian President Bashar Assad's troops and the SDF is a tricky one that shifts between cooperation, live-and-let-live and skirmishes, depending on the current situation. After Turkey launched its offensive, the Kurds struck a deal with the government that saw Syrian troops mobilized to fight the Turkish forces, allowing them to enter a region they had ceded to the SDF.

Russia has consistently backed the government of Syrian President Assad (L, with Putin in 2018) and assisted its forces. After US troops pulled out of the Kurdish areas, Russia moved its troops in to act as a buffer for Syrian government forces advancing towards the Turkish army. Moscow wants Syria to remain united and has accused the US of creating parallel structures in the Kurdish region.

Turkey also has allies among Syrian fighters. The Syrian National Army (SNA), also known as the Free Syrian Army, is a Syrian rebel group that has fought against the SDF and Assad's government. Backed by Turkey, SNA fighters took part in previous Turkish offensives against Kurdish militias inside Syria. Currently, thousands of SNA fighters are fighting the YPG alongside Turkish forces.

One possible future actor is IS. While it was essentially defeated in March 2019, tens of thousands of its fighters and their families remain in prisons or guarded camps in the Kurdish area of the country. Nearly a thousand alone have already escaped from a camp that was caught in the fighting between Kurdish militias and Turkish forces. Should the situation grow more unstable, IS could regroup.

According to UN sources almost 200,000 people have become IDPs (internally displaced people) since Turkey launched an attack on Kurdish-controlled territories on October 9. Many Kurds have reportedly tried to cross the border to seek shelter in the Kurdistan region of Iraq, but only those who can produce an Iraqi-Kurdish resident card are allowed to cross.

Many villages in Syria's northeast have nearly emptied of people over the last week. Women and children in towns close Turkey have been heading further inland, to Hassakeh, leaving the border region inhabited almost only by men. "Conditions are deteriorating rapidly in Hassakeh due to the massive flux of people, so we decided to stay," Suna, a mother of three children told DW.

The once lively bazaar in Amuda has turned into a gloomy place where just a few men gather. Many shops have folded since the Turkish invasion began, and those which remain open sell products at hardly affordable prizes due to the collapse of the Syrian currency. Shelling form the other side of the frontier usually starts at dawn, so those who remain in the town hardly venture outside at night.

Coexistence between the Syrian Kurdish administration and President Bashar Assad's regime in Qamishli, the main city in the country's northeast, has been tense since the Syrian civil war started in 2011. The recent deal between the two sides involves a redeployment of Syrian troops along the Turkish border. It is unclear who will be in control of the region in the short term.

While Kurdish combat units fight against the Turkish army and Ankara-backed militants, it's still unclear what the Syrian Kurdish fighters' status will be since reaching out to Assad for support. "We will keep controlling the area as we've done until today, there will be no substantial changes other than a joint command in certain border areas," officials told DW.

Syrian Kurds feel betrayed since the US president decided to pull out all remaining troops. Many told DW they felt relief that the Kurdish fighters had struck a deal with the Syrian regime to control the border areas as it could prevent Turkey from attacking their villages. "We know what Trump did to us, but we still know nothing about Putin's intentions," said Massud, a barbershop customer.

After decades of brutal repression under the Assads, many residents in Derik refused to comment on the possible consequences of the regime's comeback to an area that has enjoyed de facto self-rule for several years. "The whole country was controlled by the secret services back then, and it may happen again soon, so no one will dare to talk to you about it," one person said.

All over Syria's northeast residents have had to deal corpses arriving daily from the frontlines. Turkish air strikes have hit both military targets and civilians so that many hospitals caring for wounded fighters, such as the one in Derik, have been evacuated to avoid further casualties.

The Syrian Kurds claim to have lost around 11,000 people in the fight against the so-called Islamic State. Although IS has lost control over territory of any significant size, the killing continues. Dozens of civilians and hundreds of fighters have reportedly been killed since Turkey launched its attack on Syria's northeast.

The Kurds in Syria opted to side neither with the regime nor the opposition after the civil war broke out in 2011. Now they stand alone, besieged and with no one to back them since their American allies withdrew.