(CNN) A "safe zone" in Syria? The US tried it with Turkey before. It didn't work.
President Donald Trump has tweeted twice about the possibility of establishing a "20 mile safe zone" in Syria, something he has said is part of his decision to pursue a total withdrawal of US troops from Syria, a decision that sparked several high profile resignations from his administration.
Trump has also said that he was working with his Turkish counterpart, President Recep Tayyip Erdoğan, on the concept of such a safe zone, but has provided little in the way of additional details as to what exactly such a zone would look like.
"Spoke w/ President Erdogan of Turkey to advise where we stand on all matters including our last two weeks of success in fighting the remnants of ISIS, and 20 mile safe zone. Also spoke about economic development between the US & Turkey - great potential to substantially expand!," Trump tweeted last Monday.
While the details of the plan are not clear, a similar US effort to work with Turkey to help create similar such zones west of the Euphrates River foundered in 2016 after Turkey and its local Syrian allies went beyond the mission of targeting ISIS and began attacking Kurdish positions in northern Syria.
Administration officials have similarly been unable to provide any insight as to what would be involved in establishing Trump's proposed zone in north eastern Syria along border with Turkey.
"We're in the planning processes and I can't get into that," acting chief Pentagon spokesman Charles Summers told reporters Friday.
Republican Sen. Lindsay Graham, a vociferous critic of Trump's decision to pullout of Syria, said Saturday that he hopes Trump "would slow the withdrawal" of troops in Syria "until we truly destroy ISIS."
Graham made his comments at a press conference in Ankara following meetings with senior Turkish officials including Erdoğan about Syria.
He noted a potential plan between Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, and the Turkish military "that can accomplish these objectives" and aims to move Kurdish YPG elements away from the Turkish border with Syria, a possible reference to the purported safe zone.
Turkey sees the US-backed YPG as closely linked to the Kurdish separatist group known as the PKK, which has carried out attacks against Turkey. The US does not share that view.
Dunford met with his Turkish military counterpart in Brussels, Belgium, and discussed Syria and "efforts to implement the directions of their respective presidents," according to Col. Pat Ryder, Dunford's spokesman.
For his part, Erdoğan has said that Turkish forces and their local allies would take part in such an operation, which he said would target many of the Kurdish fighters backed by the US.
In a phone call with Trump on Sunday, Erdogan said his country is ready to take over security in the Syrian town of Manbij, "without delay," according to Turkey's state news agency Anadolu.
Turkey has long sought influence over Manbij, an area where an ISIS attack killed four US personnel last week.
White House press secretary Sarah Sanders issued a statement saying "the two leaders agreed to continue to pursue a negotiated solution for northeast Syria that achieves our respective security concerns," but did not provide specifics.
Erdogan said that Turkey will not allow the PKK and the YPG to destabilize northeastern Syria, again casting doubt on the fate of America's Kurdish allies in the ISIS fight should Turkey be the one to enforce a safe zone.
However, the 2016 operation, which took place west of the Euphrates, encountered major challenges due in large part to competing priorities between Ankara and Washington.
The US was initially supportive of the Turkish operation, which aimed to clear ISIS from a stretch of border area.
Backed by US airstrikes, Turkish troops, tanks and allied Syrian opposition fighters crossed the Syrian-Turkish border in August, capturing the town of Jarabulus from ISIS and pushing south and west in an effort to clear the terror group from its border.
Up to 40 US Special Operations Forces accompanied Turkish troops during the operation.
However, as the Turkish force advanced on the Syrian town of al-Bab, Turkey's local allies and Turkish troops attacked units from the US-backed Syrian Democratic Forces that were also operating against ISIS in the area.
Turkey's actions prompted the US to end its support for the Turkish operation.
"As they went across into Jarabulus, I would highlight to you that we did support that operation focused," Gen. Joseph Votel, the commander of US Central Command said at the time. "When they began to focus on something other than (ISIS) then I think we had to withdraw our support for that."
As Turkish forces struggled to retake al-Bab, even asking Russia to provide air support, US and Turkish officials reached an accord that allowed for the resumption of US airstrikes.
Trump's latest proposal of a safe zone was criticized Friday by his former envoy for the fight against ISIS, Brett McGurk, who resigned over Trump's decision to withdraw.
"Trump's latest proposal, issued via tweet, for a 20-mile safe zone — which Erdogan says Turkey will establish — similarly seems to have been made with no process or analysis. This area would encompass all Kurdish areas of eastern Syria. There is no force ready to take over, nor time to build one, as American troops prepare to leave," McGurk wrote in a column in the Washington Post.
The "entry of Turkish-backed opposition forces would likely displace thousands of Kurds, as well as threaten vulnerable Christian communities interspersed in these areas," he said, adding that "entry of the Turkish military and Turkish-supported opposition fighters into SDF areas of northeast Syria -- as is now being discussed -- would precipitate chaos and an environment for extremists to thrive."
Two US military officials have told CNN that Turkey is currently hoping "to conduct a limited offensive operation" and create a 20-mile "buffer zone" in northeast Syria, an area currently controlled by the Syrian Democratic Forces.
The officials say Turkey has stationed some 16,000 troops and 10,000 local Syrian allies to participate in the operation.
However the makeup of the Turkish backed fighters has sparked concerns among US officials that they could not be trusted to avoid attacking Kurdish groups and other US allies in the area.
"On Syria, Turkey is not a reliable partner. The Syrian opposition forces it backs are marbled with extremists and number too few to constitute an effective challenge to Assad or a plausible alternative to the SDF," McGurk wrote, referring to the Syrian President Bashar al Assad.
The Turkish-backed groups "included fighters that had formerly been part of Jabhat al-Nusra (a one-time al Qaeda affiliate), Ahrar al-Sham, and in some cases former ISIS fighters. The Syrian rebel force that Turkey put together was not vettable by the US military and was in fact a threat to the Americans because of the extremist fighters that were included in it," Nick Heras, an analyst at the DC-based Center for a New American Security told CNN.
"Turkey also did not assemble a force that was reflective of the local population, and borrowed heavily from Syrian rebel groups that were originally from northwest Syria, and was not going to be considered legitimate by the local population," Heras added,"
US military officials have expressed similar concerns to CNN and these Turkish backed proxy forces routinely shot at US troops stationed around Manbij, Syria.
"As it stands now, the force that Turkey is mobilizing for operations east of the Euphrates is just as likely to build a new transnational terrorist safe haven there, as it is to prevent ISIS from reclaiming its old one," Heras added.
The composition of these groups has led many analysts to believe that the US-backed SDF may be more comfortable cutting a deal with the Russian and Iranian-backed regime in Damascus than take its chances with Turkey.