From the Wikipedia article on the Nagorno-Karabakh Autonomous Oblast:
According to Robert Service, in 1921 Joseph Stalin, then acting Commissar of Nationalities for the Soviet Union, included Nakhchivan ASSR and Karabakh under Azerbaijani control to try and placate Turkey to join the Soviet Union. Had Turkey not been an issue, Stalin would probably have left Karabakh under Armenian control.^[2]
Wikipedia cites Stalin: a Biography by Robert Service as the source. However, according to the criticism section of his Wikipedia page his biography on Trotsky has "a host of factual errors." So can anyone knowledgeable on this topic verify the truth to this, and if it is truthful how likely Turkey could have joined the USSR?
I'm not an expert on Turkey, but rather the USSR.
I'm not able to cite anything for the proposition of a negative obviously, but I've never read anything about such an initiative by Stalin. That doesn't mean it wasn't possible he wanted to, but I find it far-fetched at best as far "was it realistic?"
In 1921, the USSR was wrapping up the Civil War with the White Army. They had also just finished up the Polish front, but were still dealing with the aftereffects of the "Siberian Intervention" and fighting in the far east. After the fairly disastrous Polish-Soviet War, which ended in March, I find it a little incredible to believe that the USSR was really making a play for Turkey, particularly given that Mustafa Kamel was just taking power and asserting Turkish nationalism.