Hans Morgenthau's power analysis combines a philosophical, explanatory and practical approach. In his philosophy, power and the will for domination constitutes the nature of politics. In his explanatory approach power, expressed in terms of interest, provides both the aim of foreign policy and the means for its achievements. The practice of power focuses on the ways states(wo)men need to gauge power to avoid miscalculus and its perils. Although filled with insight about the limits of power analysis, like the reduction of power to military affairs or the hubris of the perfect power assessment, Morgenthau's approach is profoundly contradictory. Whereas he needs an explanatory theory of power to support his meta-physical statements, ultimately, the explanatory theory is not independent of it. While his theory should explain the historical record, the somewhat given lessons of history are the defense for his theory (and hence the theory cannot be independently justified). Whereas power needs to be precisely measurable for any statement of its maximisation and balancing, as the explanatory approach requires, his practical approach insists in the sheer impossibility and political danger of believing in such precise measure, since it undermines the realist quest for prudence. This analysis will inform the early chapters of a book project on power analysis in International Relations. Morgenthau stands as an example for the awareness that power is used in three different sites at the same time, an awareness often lost in later writers. The different attempts to deal with the tensions and contradictions of using the three sites at the same time will inform the evolution of power analysis in the following chapters.