Regional security dynamics in the post-Cold War Southeast Asia are in flux. On the one hand, the intensifying Sino-US competition and, on the other hand, the rise and re-emergence of a number of other significant powers, such as Japan and India, has caught Southeast Asia at the geostrategic pivot of the evolving security order in the Indo-Pacific. As countries in Southeast Asia try to shield themselves from the possible fallout of any major power confrontation in the region, avoiding entrapment and having to choose sides, smaller powers have instead chosen to hedge their position through cultivation of multiple alignment options, or ‘strategic insurances’. This diversification of state’s strategic relations with a number of secondary and, even, tertiary powers help weaker actors in maintaining their relative foreign and security policy autonomy or strategic space in the region.

The inherent inclusivity of this strategic play, which can be characterized as omnidirectional hedging, aims at addressing the triple uncertainty in the evolving regional order: The fear of entrapment into a major power confrontation that could have serious consequences to the region’s security; abandonment by a major power patron in the face of a conflict, and; unease over overt dependency on any single major power that may hamper one’s foreign and security policy autonomy—constraining the actor’s relative strategic space. Further, the omnidirectional hedging logic addresses smaller powers’ fears of having to choose sides between the major powers, in particular between the United States and China, in the high stakes security environment.

This thesis examines the above security dynamic by studying the role of defence diplomacy in Southeast Asia in maintaining or expanding small powers’—namely the ASEAN core states: Indonesia, Malaysia, Singapore, Thailand, and the Philippines—relative strategic space. Defence diplomacy remains a relatively understudied phenomenon with much of focus on the empirical side, the emergence and roles defence diplomacy has taken in Southeast Asia over the past thirty years. There has been little or no in depth analysis of defence diplomacy’s strategic effects and utilization by weaker or smaller powers. Neither have there been attempts to situate defence diplomacy in the theoretical literature of international relations and security studies. This thesis tries to bridge those gaps by linking defence diplomacy to broader theoretical framework, in particular, to the defensive realist tradition with interest in defence diplomacy’s strategic (structural) effects on weaker actors’ security: External assistance in building the ‘minimum credible deterrence capacity’; claiming ownership of the region’s own security challenges through ‘cooperation for self-help’; and diversification of state’s alignment options (‘strategic insurances’), and, hence, defence diplomacy’s contribution to the maintenance of small power’s strategic space in the broader Indo-Pacific.

Defence diplomacy acts as an intermediary between the competing great power interests in Southeast Asia and the South China Sea. It helps improve smaller powers’ ability (understood in terms of relative material capacity) to tackle the myriad of non-traditional security challenges that emanate from the region. The ASEAN-led regional institutions, forums, dialogue mechanisms, and other initiatives facilitate the multilateral defence diplomacy interaction between the region’s small and large powers. Those arrangements, most notably the ASEAN Regional Forum (ARF) and the ASEAN Defence Ministers’ Meeting-Plus (ADMM-Plus), have facilitated the practical defence diplomacy cooperation in, especially, non-traditional security, or Military Operations Other Than War (MOOTW), including in maritime security, disaster response, and counter-terrorism, and in developing the region’s military capacity and capabilities to address those challenges.

Beyond the multilateral defence diplomacy, bilateral defence diplomacy between the ASEAN core states and their respective big power allies and partners focuses more directly on assisting the weaker states develop their capacity and capability in deterring interstate challenges, most prominently in the South China Sea. Small powers utilize defence diplomacy as a bargaining tool to enhance the region’s standing in addressing its own security challenges through sub-regional and regional mechanisms, negating the direct interference of outside powers. With the enhanced national and regional capacity and, thus, resilience, Southeast Asian core states are poised to be better equipped to address the myriad of non-traditional security challenges that permeate the region—denying outright involvement of external powers in the region’s affairs (strategic ‘push’), while diversifying their strategic bets (strategic ‘pull’) for strategic space and addressing the longer-term systemic uncertainty by cultivation of a number of alternative strategic options.