The United States and Turkey have different threat perceptions. Turkey's main threat perception - it's enemy No. 1 - has been Kurdish nationalism, terrorism with Kurdish ethnic roots. For the United States, enemy No. 1, since 9/11, has been jihadist terrorism. So up until Syria, the two countries were able to agree to disagree on their threat perceptions. But with Syria, there emerged a situation where the United States partnered up with the Kurdish terrorist group in the eyes of Turkey. And Turkey has turned a blind eye to jihadist groups in Syria by basically opening its border, and a lot of ISIS fighters entered Syria through Turkey. So this is a nightmare for Turkish-American relations.