Submarine proliferation in the post–Cold War environment has led to an exponential increase in the number of regional submarine operators and begs the question: Were these submarine purchases made for deterrence, enforcement, prestige, or a combination of the three? This thesis compared the case studies of Indonesia, Malaysia, Singapore, and Vietnam, analyzed statements made by government and defense officials, and weighed each against the regional security environment to determine states’ rationales for purchasing submarines. Indonesia, Malaysia, and Singapore likely purchased submarines for deterrence and enforcement, and Vietnam for deterrence. The deterrence imperative for all states was relatively strong, but enforcement rationales varied; prestige lacked credible evidence as a rationale for submarine purchases. Future submarine proliferators, including the Philippines and Thailand, are likely to successfully acquire submarines when the deterrence or enforcement imperatives are strongest. These findings are significant because regional submarine operations that increase the potential for undersea conflict or accidents can be minimized if governments can reduce the threat perceptions of other states or find alternative, effective methods to enforce the maritime domain.

Subjects: submarine; non-nuclear submarine; diesel-electric submarine; undersea; submarine proliferation; Southeast Asia; deterrence; enforcement; prestige; regional security