This is Christopher Catherwood's examination of the dilemma Britain faced in relations with Turkey and some of the Balkan states from 1939–41. It is largely based on a study of the British archives of the period, although he references recent work on the Soviet archives. Turkish primary sources are sadly scarce, so it is very much a view from the British side of the hill.
I didn't hold out much hope as the Turkish player of holding on. T34/85s against Valentines and Stuart tanks looked like a challenge. However, in particular, the Stuarts did well, and the Soviets lost a lot of units before they reached their objective, the prepared defences. Victory to the Red Army but only just.