Adding to the sheer size of the refugee flow is the fact that most of the refugees are Syrian Kurds, with longstanding ties to the Turkish PKK and thus seen by Turkey as a potential threat, while at the same time there have been clashes with PKK supporters seeking to enter Syria to relieve the siege of Kobanê.
Despite Western pressure, Turkey's government remains aloof from the US-led coalition, for a variety of reasons, well-stated by Henri Barkey at Foreign Policy in "How the Islamic State Took Turkey Hostage."
One bit of mystery was the sudden freeing of the 49 hostages (43 Turks and three Iraqis) held by ISIS since the fall of Mosul in June. When released a few days ago, the Turkish government credited a "rescue operation" conceived by Turkey's National Intelligence Organization (MIT), with some ill-defined "diplomatic" role and a staunch denial that any ransom had been paid. A lot of eyebrows were justifiably raised. The Turkish military also claimed role.
An article at Al-Monitor by Metin Turcan, "How and Why were 46 Turkish Hostages Freed?" I obviously cant testify to its accuracy, but among the assertions is this:
Three plans were developed for the rescue of the hostages: a military operation, persuasion through contacts with IS or paying ransom. Turkish intelligence officials were in close contact with IS in Mosul, with the Army of Naqshbandi dominated by former Baath cadres and with the Council of Mosul Tribes. The plan for a military operation was shelved after establishing close contacts with influential Sunni Arab tribes in Mosul who have been friendly to Turkey for many years. Turkey’s close liaison with the Mosul tribes was never a secret.On the curious alliance between ex-Baathists, the Naqshbandi Order, and ISIS, see my earlier post, "Strange Bedfellows: ‘Izzat Ibrahim, the Naqshbandi Order, and ISIS." I have no idea how accurate the report is, but clearly it's these sort of links between Turkey and rather sketchy elements inside Syria and that bothers many in the West.