Since it became independent in 2011, South Sudan has been confronted with ongoing security threats, internal political rifts, economic vulnerabilities and external pressures that have impeded its efforts to establish stability and achieve sustainable development. This paper critically analyses PRC’s lack of a coherent grand strategy—specifically, the ramification and coordination of military, diplomatic and economic policies necessary to build the foundation for its national security. Through a less nuanced assessment of interlocking policies (Mann’s “interlocking trinity”), the research finds that fragmented policy strands plus inner bellicosity contribute to strategic disingenuity, militarisation not peacebuilding and sustainable development. Empirically it appears that flexible and wavering policies, frequent changes in approaches to diplomacy or trade combined with resource dependence have worsened instability. On the other hand, external pressures from regional and global actors pose a threat visceral to policy cohesion, obstructing attempts for much-needed common strategic vision. The research is clear: without a coherent, well-articulated grand strategy, South Sudan will be susceptible to internal shocks and external threats that generate cycles of conflict and underdevelopment. In addressing these the study proposes to employ what it terms a quadrilateral “comprehensive” approach involving regional military, diplomatic and economic leverage via institutional reforms, inclusive dialogue and strategic planning so as to develop coherence and policy harmony. This is a necessary approach towards legitimacy, winning international backing and constructing strong institutions that can maneuver in a geostrategic environment ridden with complications. Finally, the study also confirms that a coherent and implementable grand strategy is necessary if South Sudan is to move from being a fragile state to long-term stability, peace, and development.