An article in the Mail explains it quite well. As always, Assad features big in what is happening. A lot of countries in the region want the secular Assad regime gone, to be replaced by a government more favourable for the Sunni countries in the region and the majority Sunni population of Syria. That is why Turkey turned a blind eye to Isis who are fighting Assad along with funded Jihadis from Chechnya and other countries.
Some of our top former military leaders have said that Isis cannot be defeated by airstrikes and that boots on the ground will be needed. So you have to winder why there are no boots on the ground.
"With his ambition to revive of Turkey’s once-great power status, Erdogan has allied the country not only with the conservative Sunni Muslims of Saudi Arabia, but with the Muslim Brotherhood regime of former President Morsi in Egypt, and with the Sunni militant Palestinian group Hamas.
In doing so, he destroyed Turkey’s good relations with Israel, a staunch ally of the Kurds.
It is wrong to view them differently, we need to deal with them jointly
Recep Tayyip Erdogan, Turkish president, speaking of the Kurds in Kobane and Islamic State
Relations with the newly elected military regime in Egypt are grim, too. Erdogan’s emotional pull towards Sunni Arabs means he is implacably opposed to Syria’s President Assad, who is an ally of Shia Iran, and explains why he is so keen to back Assad’s enemies, even if that means backing IS.
That is why he is telling the U.S. that only if America extends its intervention in Syria to toppling Assad will he move a muscle to help the Kurds in Kobane.
Erdogan will drive a very hard bargain before he contemplates any military action, not least because the Turks realise that while Western intervention comes and goes in the Middle East, Turkish intervention in Syria could involve the country in an intractable war that lasts decades.
This, then, is the country which the West hopes will put men on the ground to repulse IS.
Some hope. For as well as supporting the terrorists, Turkey has been allowing British jihadis to cross its borders, while simultaneously claiming to join the anti-IS coalition."
www.dailymail.co.uk/news/article-2787303/Prejudice-hatred-Turkey-won-t-barbarians-border.html