This paper aims to critically examine the change of Michel Foucault’s power theory “from war to governmentality” in the College de France lectures from 1976 to 1979. In that period, Foucault had attempted to change his own conception of power from discipline to bio-power, from bio-power to governmentality, and from neoliberal governmentality to the ethics of self. This paper focuses on the second change in order to track the change of power theory in Foucault. This change serves as a very important link in the development of Foucault's power theory. It not only incorporates disciplinary power and bio-power into a more expanded problematic of security power and liberal governmentality but also serves as an important stage for shifting beyond neoliberal governmentality and technologies of self into self-care and self-cultivation. In particular, this shift reflects the changes in the intellectual and political area in France as well as in Foucault's own theoretical practices. In that time, Foucault started to be more interested in liberalism while distanced from radical leftists and Marxists, who had together participated with Foucault in the social struggles since the ’68 Revolution. Considering these changes, this paper tries to grasp the turn “from war to governmentality” in the development of Foucault’s power theory.