The relationship between Turkey and Russia has transformed from open hostility during the Cold War to compartmentalization in the 2000s, and competitive cooperation during the last decade. These developments created concern among Turkey’s allies who started wondering if Turkey was changing axis or being lost to Russia. Turkey’s acquisition of S-400 air and missile defense systems from Russia has led to one of the deepest crises between Turkey and the United States. Interestingly, this evolving relationship between Turkey and Russia seems to survive despite the battle in Idlib between Turkey and the Russian-backed Syrian regime forces. What are the main drivers of the Turkey-Russia relationship? What are their converging and diverging interests? What is the scope and limit of this relationship, and what is its personal dimension? And, what are the implications for Turkey’s transatlantic allies?