"Turkey, a longtime NATO ally, is of significant relevance to U.S. interests, largely owing to its status as a constitutional republic with a large, diversified economy and a Muslim-majority population that straddles Europe and the Middle East. The history of the U.S.-Turkey relationship is replete with complications. Bilateral ties have experienced a period of particular stress over the past five years in connection with conflict in Syria and Iraq, increasing domestic contention in Turkey, and the continuing consolidation of power by President Recep Tayyip Erdogan. Nevertheless, Turkey continues to allow the United States and other members of the coalition assembled to fight the Islamic State (IS, also known as ISIS/ISIL) to use Turkish territory for airstrikes against IS targets."
CRS Report for Congress, R44000
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html