This thesis attempts to demonstrate the evolutionary character of American nuclear doctrine from the beginning of the nuclear age in 1945 until 1980. It also aims at disclosing some of the most important factors that contributed to the doctrine`s evolution, namely, technological progress and developments in weaponry and the shifts that were taking place in the correlation of forces between the two superpowers, the Soviet Union and the United States. The thesis tries to establish the relation, if any, between these two variables (technology and balance of forces) and the evolution of the doctrine from Massive Retaliation to limited nuclear war. There are certainly many other factors which influenced military doctrine, but this thesis focuses on the above mentioned factors. touching on others when it was thought essential.The thesis concludes by trying to answer the question of whether the purpose of the limited nuclear war doctrine is to keep the initiative in US hands, that is putting itself on the side with the positive purpose, or not. Refs.