Power transition theory (PTT) has effectively explained the concept of war among great-power states and has successfully competed with the balance of power theory since Organski proposed it in 1958. PTT’s main argument is as follows: when one state’s power approaches that of another state and it is dissatisfied, it is highly likely that the state will initiate war. Lemke (2002) further applies PTT to regional wars and argues that PTT is powerful in explaining both hegemonic wars and regional wars. This paper follows Lemke’s definition of regional dyads and focuses on Northeast Asia.