A decade ago it was possible to argue with some confidence not only that the Soviet Union and the United States had spheres of influence but also that they had a tacit understanding about them. The existence of a tacit understanding seemed to be confirmed, for instance, at the time of the invasion of Czechoslovakia in 1968, in that while the United States denounced the Soviet action it nevertheless acquiesced in it. At that time it could be claimed that the Soviet Union had merely acted in eastern Europe in the same way as the United States had on various occasions in Latin America, the most recent being the intervention in the Dominican Republic in 1965. Further, the doctrines each power used to justify intervention were alike. The Brezhnev Doctrine justifying the intervention in Czechoslovakia seemed similar to the Johnson Doctrine legitimizing intervention in the Dominican Republic in that both claimed hegemonic rights within a sphere of influence. And from this a reciprocal understanding was inferred about what each would allow the other to do in its respective sphere. Both superpowers denied it. The United States did so because spheres of influence transgress the doctrine of the sovereign equality of states and because the practices associated with them violate the norms of interstate behaviour. The Soviet Union did so because it counterposed the Soviet Union to other socialist States and it would have followed that the Soviet Union would not have been acting, as it claimed, in the interests of socialism.