This article presents a theoretical approach of analysis and estimate of the influence of military change on international relations, as well as the interpretations of the impact of military change on international systems during various historical periods. The first part of the paper defines the term of the fundamental military change and the cycle of the fundamental military change in the international system; it also presents some insights of the offense-defence balance theory with the estimate of the impact of military change on international relations. The second part of the article describes various cases of the influence of fundamental military changes on the international system until the invention of the nuclear weapon (the revolutions of artillery, firearms and naval warfare from the 15th until the 17th c.). The chapter on the nuclear era provides an analysis about the role of military changes during and after the Cold War, i.e., in the contemporary international system. This article explains that until the invention of the nuclear weapon, fundamental military changes could determine the survival of a state and could provide it with exceptional opportunities to establish its power over other states. Meanwhile, during the nuclear era the impact of military transformations became much more subtle. It is claimed that during the Cold War military changes played the role of balancing the bipolar international system, whereas, after the Cold War the influence of such changes became destabilizing.