The US is on the verge of what some observers will describe as a historic betrayal of an ally.

Kurdish fighters in northeast Syria were instrumental in crushing the so-called Caliphate of Islamic State that took root in the country. Armed by the US, they were the essential ground troops, and endured the deaths of tens of thousands of fighters, in the operation. Turkey, however, claiming it fears a strengthened “terrorist” Kurdish insurgency, wants them cleared from border areas—and after an October 6 phone call with Turkish President Recep Tayyip Erdogan, Commander-in-Chief Donald Trump agreed to abandon them to allow Ankara to pursue that objective unhindered.

The Turkish lira (TRY), at around 19:30 Istanbul time, was trading 2.4% weaker against the dollar at 5.8346. The depreciation gained pace after Trump, under fire from left and right for his Syria decision, tweeted that, “As I have stated strongly before, and just to reiterate, if Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey (I’ve done before!)”.

The main Kurdish-led group, the Syrian Democratic Forces (SDF), has called the sudden US move a "stab in the back".

“Disaster in the making”

US Republican Senator Lindsey Graham, a close ally of Trump on many issues, said the announcement was a "disaster in the making", adding that he would introduce a Senate resolution opposing the decision and calling for it to be reversed. Graham also remarked, to Fox News, that the move represented “a big win for Iran and [Syrian President Bashar al-Assad [and] a big win for Isis [Islamic State]”. “Isis is not defeated. This is the biggest lie being told by this [Trump] administration,” Graham said.

Mustafa Bali, a spokesman for the SDF, which occupies former Islamic State territory in northeast Syria and includes the Kurdish YPG militia, said: "It seems that the policy of the United States is to betray their friends and allies". The US, he said, was allowing the territory to “turn into a war zone”. The SDF would “defend northeast Syria at all costs”, he ominously added.

Kino Gabriel, another spokesman for the SDF, told Arabic TV station al-Hadath: "The [US] statement was a surprise and we can say that it is a stab in the back for the SDF."

Badly needs some successes

Erdogan badly needs some successes that score well with Turkish voters. He’s widely seen to have botched the Turkish economy, leading it into a currency crisis that resulted in a biting recession, and Turks have been making their displeasure known in local elections, while former top members of the president’s party have split off to form their own parties with an eye on dislodging the newly vulnerable Erdogan. Trump has previously not backed Erdogan’s longstanding plan for a Turkish incursion across the border. Why he has changed his mind now is not clear.

One outcome of the call is that Erdogan is expected to visit the White House next month. The understanding is that he promised Trump Turkey would take over responsibility for Islamic State prisoners once it has secured targeted territory in the Syrian region.

However, Brett McGurk, former US special presidential envoy for the coalition against Islamic State, said on Twitter that the announcement of the US pullout demonstrated a "complete lack of understanding of anything happening on the ground" and noted that the US was not actually holding any Islamic State detainees. They are, he said, being held by the SDF, “which Trump just served up to Turkey”.

“Reckless gamble”

“Turkey has neither the intent, desire, nor capacity to manage 60,000 detainees, which State and [Pentagon inspectors general] warn is the nucleus for a resurgent Isis [Islamic State]. Believing otherwise is a reckless gamble with our national security,” McGurk said.

Prior to his phone call with Trump, Erdogan had complained that the Americans were dragging their feet over establishing a “safe zone”, cleared of Kurdish forces, extending around 25 kilometres from the Turkish border. The deal for the zone was meant to render plans for a Turkish military offensive unnecessary.

But the White House did not mention that deal in its statement following the phone discussion. “Turkey will soon be moving forward with its long-planned operation into northern Syria,” the statement said. “The United States armed forces will not support or be involved in the operation, and United States forces, having defeated the Isis [Islamic State] territorial ‘caliphate’, will no longer be in the immediate area.”

No sentiment for the Kurds

Trump attempted to justify his move with a series of tweets on October 7.

He brooked no sentiment for the Kurds, writing: “The Kurds fought with us, but were paid massive amounts of money and equipment to do so. They have been fighting Turkey for decades. I held off this fight for almost 3 years, but it is time for us to get out of these ridiculous Endless Wars, many of them tribal, and bring our soldiers home.”

“The US was supposed to be in Syria for 30 days, that was many years ago. We stayed and got deeper and deeper into battle with no aim in sight,” he also tweeted. Trump added that the Europeans wanted the US to keep the Islamic State detainees, many of whom are European citizens, and “hold them in US prisons at tremendous cost … thinking, as usual, that the US is always the ‘sucker’ on Nato, on trade, on everything”.

Turkey regards the YPG as an extension of the banned Kurdistan Workers' Party (PKK) which has fought for Kurdish autonomy in Turkey for three decades, though the YPG denies any direct links.

Speaking to reporters on October 7, Erdogan said the Turkish military was ready to start operations in northeastern Syria at any moment. "It is absolutely out of the question for us to further tolerate the threats from these terrorist groups," the Turkish leader said, in reference to Kurdish fighters.

Erdogan spokesman Ibrahim Kalin said on Twitter on October 7 that Turkey will continue to fight against Islamic State and will not allow it to return "in any shape and form."

‘Highly likely’ to wait for US withdrawal

Meanwhile, a senior Turkish official told Reuters on October 7 that Turkey was highly likely to wait until US soldiers have withdrawn from the area where Ankara plans to carry out a military operation in northern Syria before launching an offensive. He said that the withdrawal of US forces from the planned area of operations could take one week and that it was very probable that Ankara woulf wait for this in order to avoid “any accident”.

In further criticism of Trump’s decision, former US Ambassador to the UN Nikki Haley responded that the Kurds "were instrumental in our successful fight against" Islamic State in Syria. "Leaving them to die [is] a big mistake," she added.

Another angle on the Turkish move into northeast Syria relates to how Erdogan is seeking more than $26bn in aid to build houses for about 2mn Syrian refugees currently hosted by Turkey that he hopes to resettle in the “safe zone”. That would reduce the burden on Turkey’s economy posed by the refugees and,  as Wolfango Piccoli, co-president at Teneo Intelligence, said on October 7 in a note referring to Erdogan’s ruling AKP party: “The housing project envisaged by the Turkish authorities [is a] possible bonanza for Turkish construction firms close to the AKP”.

Shares in Turkish cement and construction firms were up following the news of the US stepping aside.  

“Irrelevant occupier”

Iran's foreign minister described the US as an "irrelevant occupier in Syria", and called for respecting Syrian territorial integrity. "US is an irrelevant occupier in Syria—futile to seek its permission or rely on it for security," Mohammad Javad Zarif tweeted. "Achieving peace & fighting terror in Syria will only succeed thru respect for its territorial integrity & its people."

Iran is aligned with Assad and there are fears that the abandoned Kurds could now similarly form an alliance with Damascus, opening up the possibility of further conflict should they fight to regain the territory for the Assad regime in return for security guarantees and military backing.

In Russia’s initial reaction to developments, Dmitry Peskov, spokesman for the Kremlin, which also militarily supports Assad, said: "Turkey may take action to ensure its security, meaning resistance to terrorist elements that may be hiding in Syria,"  But, he underlined, "first and foremost we say that the territorial and political integrity of Syria must be observed."