The idea of power transition, or power shift, has recently been much in vogue in scholarly, policy, and even popular discourse. It has, for example, motivated a resurgent interest in the power-transition theory and the danger of the so-called Thucydides trap. China’s recent rise has especially motivated an interest in these topics, engendering concerns about whether this development means that China is on a collision course with the United States. These concerns stem from the proposition that the danger of a system-destabilizing war increases when a rising power catches up to a declining hegemon and challenges the latter’s preeminent position in the international system. Thucydides’s famous remark about the origin of the Peloponnesian War, claiming that “it was the rise of Athens and the fear that this inspired in Sparta that made war inevitable” in ancient Greece, has frequently been invoked to support this view. Whereas power shift is a generic term referring to any change in the balance of capabilities between two or more states, power transition is a more specific concept pointing to a reversal of positions whereby a rising latecomer overtakes a previous dominant power in the international system (or at least when this latecomer approaches power parity with the dominant power). Power-transition theory presents a contemporary version of Thucydides’s explanation of the Peloponnesian War. It calls attention to the changing power relationships among the world’s major states and provides a seemingly cogent framework to understand the dynamics that can produce war between these states and their respective allies.
A careful reader will immediately find the preceding paragraph unsatisfactory as it contains several important ambiguities. For instance, what do we mean by “major states” or “great powers,” and what do we have in mind when we refer to changes in their relative “power”? Also, does the power-transition theory claim that war is likely to break out when there is a change in the identity of the world’s most powerful country? Or does it also say that war is likely to occur even in the absence of a late-rising state overtaking, and therefore displacing, an incumbent hegemon? If so, how closely does the late-rising state have to match the incumbent’s power capabilities before the power-transition theory predicts a war between them? Would the latecomer have to reach at least 80%, 90%, or even 95% of the incumbent’s power before an approximate parity between the two is achieved? Does the power-transition theory pertain only to the relationship between the world’s two most powerful states, or does it apply to other states? And if power transition is a necessary but insufficient condition for war, what are the other pertinent variables and their interaction effects with power shifts? Finally, what do we mean by war or systemic war? The answers to these questions are not self-evident. How they are dealt with—or not—is in itself suggestive of the power relations in the world being studied by scholars and these scholars’ positions in this world and their relations to it.
Modeling of Power Transition in Full Power Shift of Hydromechanical Transmission