The historians of Russia generally interpret the Mongol conquest and yoke as a diabolus ex machina, an external factor, which interrupted or distorted the natural, internal logic of Russian historical development. This chapter deals with only one aspect of the general problem of the Tatar Yoke and the changes in Russian society and life induced by it. The traditional and largely correct interpretation has been that, for mediaeval Russia, the supreme image of absolute power and rule was the Byzantine emperor, the basileus, the 'tsar'. There was a fundamental difference, however, between the basileus and the khan. The one was the orthodox Christian emperor ruling over all men insofar as the world was a Christian society; the other was a pagan or, even worse, from the fourteenth century on, a Moslem infidel. Professor Vernadsky ends his monumental work with the statement that autocracy was part of the price Russia had to pay for survival under the Tatars.