The ambitious plan of President Recep Tayyip Erdogan of Turkey to resettle at least one million Syrian refugees within a “safe zone” along the Turkish-Syrian border has come a step closer to being realized. On Sunday President Trump endorsed a Turkish military operation to carve out the “safe zone” in northeastern Syria, currently controlled by the United States-supported, Kurdish-led Syrian Democratic Forces.

Turkey has long demanded a buffer zone along its border with Syria to check Kurdish nationalist aspirations, which it considers a grave security threat. Mr. Erdogan reframed the idea of the buffer zone in humanitarian terms, as a haven for millions of Syrian refugees currently in Turkey. Mr. Erdogan has long supported this population, but it has now became a political liability for his government, driving widespread nationalist anger and costing his Justice and Development Party votes in local elections in March.

Resettling the Syrian refugees across the border would ease this pressure on Mr. Erdogan and his government. But there is another goal as well. Ankara has consistently opposed the emergence of any Kurdish-led autonomous region in northeastern Syria. An influx of displaced people from other parts of Syria would create a living, breathing demographic barrier to Kurdish autonomy.

Despite Turkey framing the move as an effort to mitigate a humanitarian crisis, Mr. Erdogan’s resettlement plan risks creating a far larger one. The history of similar resettlement policies shows that they can be brutally effective from the perspective of the governments orchestrating them. But such policies almost always end badly for the ordinary people caught up in them. These policies create suffering for the people being moved and even greater suffering for the people whose land others are being moved to.