This article aims at clearing up a widespread misunderstanding in previous research that the classical strategic perspective, based on the writings of Carl von Clausewitz and his contemporary followers, shares ontological assumptions with realism. Although both perspectives perceive a constant state of disharmony in international politics, they differ substantially in their assumptions about state-centrism, actor behaviour, and the role of unpredictability. As the relationship between the perspectives is ambiguous, the article argues that scholars should treat them as two separate theoretical entities. The greater scholarly relevance of the article lies in its contribution to conceptual clarity.