Last month, the Turkish government unveiled the details of a controversial plan to manage Syrian refugees sheltering in Turkey. The solution: sending at least a million of them back over the border into Syria.

“Let’s carry them to the safe zones there,” Turkish President Recep Tayyip Erdogan said in Ankara as he described the plan, which would resettle refugees in a 20-mile-deep area on the Syrian side of the two countries’ border.

Now, as Turkey launched a military operation against U.S.-allied Kurdish forces in northeastern Syria on Wednesday, human rights advocates are raising alarm that any plan to resettle refugees there could ignite a humanitarian disaster and amount to a major breach of Turkey’s obligations to international refugee protections. The concept of the safe zone has been adapted in part from Erdogan’s earlier plans to create a buffer zone to protect the Turkish border.

Gerry Simpson, associate director in Human Rights Watch’s crisis and conflict division, said that designating a specific area as a safe zone is “a very dangerous undertaking.”

There would be major obstacles to keeping such an area safe, he said, including determining whether it should be designated as a no-fly zone, deciding who would police it and ensuring that armed groups are kept separate from civilians.

“The context in Syria is so complicated and unforeseeable, with so many warring parties vying over so many conflicting interests, that it’s extremely hard to imagine any zone, let alone one that stretches 500 kilometers [310 miles] from east to west, being safe enough for people to live a protected life,” he said. “There are many historical examples where safe zones have become death traps."

In one of the most notorious instances of a failed attempt to keep civilians safe in conflict, Bosnian Serb troops raided the town of Srebrenica in July 1995, executing about 8,000 Muslim men and boys over the course of several days. Srebrenica was one of six zones the U.N. Security Council had designed as “safe areas” in 1993.

“All too often in the history of mass atrocities, [a safe zone] doesn’t become a safe zone, it becomes a dumping ground or makes civilians more vulnerable,” said Simon Adams, executive director of the Global Center for the Responsibility to Protect, an independent organization focused on the prevention of mass atrocities.

Turkey’s plans to create a safe zone inside Syria, Adams said, “sounds like a killing zone dressed up in some humanitarian language.”

The U.S.-backed Syrian Kurdish forces are among Washington’s most important allies in the fight against the Islamic State, but Turkey sees them as terrorists working alongside Turkey’s Kurdistan Workers’ Party, known as the PKK.

“Our mission is to prevent the creation of a terror corridor across our southern border, and to bring peace to the area,” Erdogan tweeted Wednesday, as Turkish forces launched their offensive against the Kurdish fighters in northeastern Syria.

Days earlier, the White House announced that it would withdraw U.S. troops from the area, igniting fury on Capitol Hill, where lawmakers accused the Trump administration of abandoning the Kurdish fighters, who are responsible for guarding a network of detention centers holding Islamic State suspects and their families. But Trump has defended his decision to remove the U.S. troops, saying they “should have never been there in the first place."

“Turkey is now responsible for ensuring all ISIS fighters being held captive remain in prison and that ISIS does not reconstitute in any way, shape, or form,” Trump said in a statement later Wednesday. The Islamic State is also known as ISIS.

On top of concerns that civilians will soon be sent to unsafe areas inside Syria, advocates voiced alarm this week that civilians already there also could find themselves trapped inside Turkey’s offensive, falling victim to shelling or airstrikes.

Turkey hosts millions of Syrian refugees and is eager to reduce that burden as it faces an economic crisis at home.

A humanitarian working in the region who spoke on the condition of anonymity because of the sensitivity of the situation described the area Erdogan plans to establish a safe zone as a dangerous “no man’s land.”

“I don’t think anything about that place will be safe,” the aid worker said. In addition to safety concerns, they said the area lacks the infrastructure to house up to a million new people. “Moving people in will be easy, but then what will they do? They will be exposed to harsh winter and summer conditions,” they said. “There is no infrastructure and absolutely no economic opportunities. That to me is a recipe for disaster.”

Dareen Khalifa, a senior Syria analyst at the International Crisis Group, said Erdogan hopes to tip the balance of power in Syria’s Kurdish areas, clearing them of Kurdish fighters before repatriating Syrians there.

But many of those who could be resettled in this Kurdish region will not go willingly and would not be Kurdish, Khalifa said, describing Erdogan’s plans as essentially amounting to “socially engineering the demography to be predominantly Arab and Turkey-leaning.”

“It’s problematic on so many levels,” she said.

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