Responding to ISIL / ISIS advances in Iraq & Syria is complicated by the stance of Turkey, why is complicated. That a NATO member has provided support, even sanctuary is a reminder of how Pakistan (via ISI) followed its national interests over Afghanistan.

Turkey regards itself as nation that stands as a bridge between Europe, Asia and the Middle East. It has been a longstanding NATO member, which has provided bases to the USA, sometimes with restrictions even a veto on use like today and before in the Second Gulf War.

A Washington "insider" last week commented that Turkey's stance on ISIS / ISIL as a NATO member was very hard to understand and accept for the USA.

Today I found two different, complimentary articles:

a) Turkey’s ISIL crisis is worse than you think:http://america.aljazeera.com/opinion...evantisil.html

After two years of tolerating the group as it funneled recruits and supplies into Syria, Turkey has come to the realization that the group represents a serious threat to its national security. How did Turkey get into such a predicament?
b) Turkey and the "Islamic State”:https://www.opendemocracy.net/vicken...state%E2%80%9D

Turkey is notably reluctant to join a military campaign against ISIS. In fact, Ankara's ambiguity towards the radical Islamist group has deep political as well as historical roots.
SWC / SWJ has three directly relevant threads:

1) Turkey in Syria: new flashpoint:http://council.smallwarsjournal.com/...ad.php?t=20263

2) Why Syrians in Turkey are Not “Refugees” and Why it Matters:http://smallwarsjournal.com/jrnl/art...why-it-matters

3) Turkey mainly, Iraq and the Kurds (2006-2012):http://council.smallwarsjournal.com/...ead.php?t=3104

Following the seizure by ISIS of forty plus Turkish diplomats @ Mosul, Turkey refrained from a hostile response. This week the hostages were exchanged for a larger number of ISIS prisoners.

Some expect this will enable Turkey to change its stance. I am unconvinced. The roots of their stance are deep and criticism can be deflected by their acceptance of millions of refugees, with 130k Kurds this week.