-
In the specific case of TR (read: Mediterranean) Stalin was simply following the traditional policy of Russia as put by Pyotr Velikiy and his successors. So, I'm confident that he wasn't just predating upon the poor and weak neighbour but making it an opportunity to advance "downwards". If it wasn't for his ex-allies that "secured" Iran and eventually Turkey, I'm sure he would act. (I'm talking about post-1945 though...)
-