In the aftermath of a surprise announcement to withdraw American troops from Syria this week, US president Donald Trump has faced criticism from allies at home and abroad for threatening to derail the fight against Isis.

But of far greater concern for the Syrian Kurds currently on the frontline of that battle is the threat of an attack by Turkey, the likelihood of which has now increased significantly.

“There are serious risks from Turkey implementing its threats,” said Mustafa Bali, a spokesperson for the Syrian Democratic Forces (SDF), the Kurdish-led group backed by the US and currently fighting against Isis.

“There are fears among civilians of massacres and displacement. There are over three million people in this region, and they are at risk,” he told The Independent.

The Kurdish and Arab militia has been a key US ally in the fight against Isis. For the past three years, Washington has backed the group with military aid, air strikes, and sent 2,000 troops to support them on the ground. Together they have captured nearly all of the territory once held by the extremist group.

In the areas of northern and eastern Syria it now holds, the SDF has built the foundations of an autonomous administration that it hopes will outlast the country’s civil war.

But US support for the group has angered Turkey, a fellow Nato member, which sees the Kurdish fighters that make up the majority of the SDF as terrorists and a threat to its own stability. Turkey’s president Recep Tayyip Erdogan has repeatedly threatened to launch a cross-border incursion, along with allied Syrian rebel fighters, but the presence of US forces has prevented such a move.

The abrupt withdrawal of US troops, announced without the coordination with the SDF, may have changed that. One western diplomat told The Independent that prior to Mr Trump’s announcement, they had expected Turkey to take action east of the Euphrates at some point, “but carefully”.

“Now I think they will go in but bigger. I think they will want to go as soon as possible, before the regime and the YPG (People’s Protection Units) make a deal, so they can grab as much land as possible,” they said.

On Friday, Mr Erdogan reiterated his intention to take action in Syria, but appeared to delay the start of the operation at least until US forces have fully withdrawn. US officials have estimated that could take between 60 and 100 days.

“We had decided last week to launch a military incursion into the east of the Euphrates River and shared that information with the public. Our phone call with President Trump, along with contacts between our diplomats and security officials and statements by the United States, have led us to wait a little longer,” Mr Erdogan said.

There are fears among civilians of massacres and displacement. There are over three million people in this region, and they are at risk Mustafa Bali, spokesperson for Syrian Democratic Forces

“Obviously, this is not an open-ended waiting period,” he added. “Over the next months, we will adopt an operational style geared towards eliminating PKK-PYD elements and Isis residues.”

Responding to news that Kurdish fighters were digging trenches on the Syrian side of the border in anticipation of a Turkish attack, Turkey’s defence minister Hulusi Akar said the fighters would be “buried in their ditches when the time comes”.

It would not be the first time Turkey has taken on Syrian Kurdish fighters. At the beginning of the year, Turkey forced the SDF out of the Afrin region, west of the Euphrates, installing its Syrian rebel allies and sending tens of thousands fleeing.

Turkish officials have said they aim to clear the entire Syria-Turkey border of fighters belonging to the YPG, who make up the bulk of the SDF. The group is linked to the outlawed PKK, a Kurdish militant group that has fought against the Turkish state for more than three decades.

Mr Trump’s announcement on Wednesday sent diplomats, military and defence officials scrambling to explain the move. One serving member of the US-led anti-Isis coalition told The Independent they were caught “off-guard” by Mr Trump’s tweet announcing the withdrawal.

Members of the SDF, who have worked closely with the US military over the past four years, were also taken aback.

“I heard about it when it was released in the press. It was very shocking,” said Mr Bali, the SDF spokesperson. “It goes against the commitments of the US and the commitments of the international coalition.”

Western fighters join Kurds in battle against Isis Show all 9 1 /9 Western fighters join Kurds in battle against Isis Western fighters join Kurds in battle against Isis Foreign Fighters A 67-year old foreign fighter from Canada, nick-named by Kurdish fighters as Hewal Zinar, poses for a photo on April 19, 2015 Uygar Onder Simsek / AFP Western fighters join Kurds in battle against Isis Foreign Fighters A 23-year old fighter and ex-US marine from the US, nick-named by Kurdish fighters as Hewal Agir, guards a look out point during clashes with Islamic State (IS) group fighters on April 17, 2015, in the outskirts of the north-western Syrian town of Tal Tamr AFP Western fighters join Kurds in battle against Isis Foreign Fighters A 26-year old from the US, nick-named by Kurdish fighters as Hewal Dilsad, shows a picture of his wife and son as he poses for a photo on April 14, 2015, in the outskirts of the north-western Syrian town of Tal Tamr Western fighters join Kurds in battle against Isis Foreign Fighters Ex-US marines aged 23 and 24 from the US, nick-named by Kurdish fighters as Hewal Agir (R) and Hewal Agit, guard a position during clashes with Islamic State (IS) group fighters on April 17, 2015, in the outskirts of the north-western Syrian town of Tal Tamr AFP Western fighters join Kurds in battle against Isis Foreign Fighters A group of international foreign fighters pose for a photo on April 16, 2015, in the outskirts of the north-western Syrian town of Tal Tamr AFP/ Getty Images Western fighters join Kurds in battle against Isis Foreign Fighters A foreign fighter poses for a photo with a machine gun on April 19, 2015, in the outskirts of Tal Tamr AFP Western fighters join Kurds in battle against Isis Foreign Fighters A 28-year old foreign fighter from the UK, nick-named by Kurdish fighters as Hewal Baran, poses for a photo on April 19, 2015, in the outskirts of the north-western Syrian town of Tal Tamr, north of Hasakeh AFP/ Getty Images Western fighters join Kurds in battle against Isis Foreign Fighters A 21-year old from the UK and 23 year-old from the US nick-named by Kurdish fighters as Hewal Sores (L) and Hewal Agir guard a post on April 19, 2015 AFP/ Getty Images Western fighters join Kurds in battle against Isis Foreign Fighters A 67-year old man from Canada and a 40-year old from the UK, nick-named by Kurdish fighters as Hewal Zinar (L) and Hewal Cudi train on April 19, 2015, in the outskirts of the Tal Tamr AFP

Before his shock announcement, Mr Trump had expressed a willingness to leave Syria, but had been convinced by defence officials that US presence was necessary to counter Iranian influence and finish off Isis.

Even so, the Syrian Democratic Council (SDC) met with the Syrian government for the first time this year as it began to consider a future without the US. Those talks fell apart, however, and the SDC received assurances from the US that they weren’t leaving any time soon. ​

Sinam Mohamad, the US representative of the SDC, the civilian administrative body of the SDF, said the timing was extremely damaging.

“During our meetings in Washington, we were told they would stay in Syria until Isis is finished, until there is stability in the area, until we have a political process,” she told The Independent by phone from northern Syria, where she was on a visit.

“We are asking why it should happen like this, so suddenly, at the same time Turkey threatens our people.”

All people in northern Syria – the Arabs, the Kurds, the Syriac Christian people – they are worried Sinam Mohamad, US representative of Syrian Democratic Council

“All people in northern Syria – the Arabs, the Kurds, the Syriac Christian people – they are worried,” she added. “They used to trust the US, but now they are very angry. They are asking me, because I am in Washington: ‘What happened, what is going on there?’”

The move appeared come as a shock to many in Mr Trump’s own administration. Just a day after it was announced, US defence secretary James Mattis resigned in opposition to the pull-out. In his resignation letter, he referenced his strong views “on treating allies with respect”, an apparent reference to the way in which Washington’s Kurdish allies were abandoned.

The withdrawal has also left Washington’s western allies in a quandary. Both the UK and France have forces in Syria alongside US troops. Their future there is now in question.

Lloyd Russell-Moyle, Labour MP for Brighton Kemptown who visited Kurdish-held Syria earlier this year, said he had tabled a motion calling on the foreign minister Jeremy Hunt to provide answers about Britain’s future role in Syria.

“The US should be leaving Syria in a planned way, not one that creates a vacuum for Turkey and its Sunni extremist militias to fill,” he told The Independent.

“Leaving before security arrangements between Damascus and the SDF have been brokered constitutes a betrayal of our Kurdish allies, who have been essential in our fight against Islamic State. It means a longer war and more bloodshed.”

France’s defence minister meanwhile called the pull-out “an extremely grave decision”.

“We do not share the analyses that the territorial caliphate (of Isis) has been annihilated,” Florence Parly said Friday on RTL radio. “We think ... The job must be finished.”

Later the same day, French president Emmanuel Macron received a delegation of Kurdish politics from the Syrian Democratic Council, who urged France to fill in the gap left by US support.

There is now speculation that the SDF may have to go and begin negotiations with the Syrian government again and give up the autonomy it has won over the past few years in order to stave off a Turkish attack.

Support free-thinking journalism and attend Independent events

Meanwhile, the fight against the last remnants of Isis continues in a small pocket of territory on the eastern banks of the Euphrates in eastern Syria.

Isis has been putting up fierce resistance in its last redoubt – a string of villages in Deir ez-Zor near the town of Hajin. After three months of intense fighting, the SDF announced last week that it had taken most of the town. But the US withdrawal has drawn attention from that fight.