Soviet government has sometimes actively assisted communist movements elsewhere, at other times been passive. The Soviet Union has been nominally one of two superpowers at least since the early 1950s, but in reality only since the late 1970s. The Soviet leaders however strongly deny that their policies amount to Russification. They explain the predominance of Russian personnel in non-Russian regions as a consequence of the lower level of culture of the other peoples. Soviet doctrine repudiates all universal morality, and maintains that the only supreme criterion is the interest of the working class. 'Cold war' has come to mean a western, principally of course American, policy of hostility to the Soviet Union short of shooting.