Turkey has long sought an internationally-imposed series of "safe zones" in northern Syria to house refugees, as a way to limit the number of refugees who actually end up crossing into Turkey. The White House resisted, fearing it would be too complicated, and President Trump's intention to shift Syria policy toward fighting ISIS made it seem like the idea was very unlikely.

Instead, President Trump made a surprise move, and is expected to order the State Department and Pentagon to prepare for the establishment of safe zones in Syria, giving them 90 days to provide a full blueprint for how they would go about it.

Arguments over the theoretical viability of such safe zones centered on the question of airspace control, with Turkey arguing the zones would be meaningless without a no fly zone, and Pentagon officials warning at the time that would mean war with both Syria and Russia.

During the campaign, Trump had endorsed the idea of safe zones on humanitarian grounds, but also scorned Hillary Clinton for supporting the no-fly zone aspect, citing the concerns about starting such huge new wars.