Despite great progress in theorizing on the causes of war during the second half of the 20th century, our understanding of international conflicts remains at an elementary level. However, Power Cycle Theory, compared to other related approaches, has raised hopes for a clear and methodical causal explanation. This theory puts decision-making about wars in the context of the rise and decline of the relative power of states and tests the effect of long-term nonlinear changes or critical points in the relative power of a state on its tendency toward large-scale wars experimentally. The question is whether there is a significant correlation between the occurrence of these critical points on the power cycle and the occurrence of war between the great powers? The research hypothesis is that the probability of a major war is higher in critical periods than it is otherwise, because of sudden shock caused by the changes in the balance of power and the role and dominance of uncertainty, as well as misunderstanding and miscalculation among the statesmen. In this study, the statement will be tested. The relative capabilities of the great powers have been assessed using the updated data from the “Correlates of War Project” (COW) during the interval 1816-2012. Moreover, the timing of critical points on each countries power cycle is compared with the occurrence of war between the major powers. The findings support the hypothesis that war is more likely to occur during critical periods than it is during normal periods.