The concept of ontological security has grown extensively in the International Relationsliterature, owing to the new explanations it generates for states’ security- and identity-relatedbehavior. In the process, however, the concept has become sprawling, vague and incoherent,due to the multitude of different understandings of the concept. To improve the concept’sadequacy, counter the risk of conceptual stretching, and provide the foundation for a commonresearch agenda, this essay constructs a typology to divide and classify the ontological securityliterature in IR. The typology’s main contribution is the dimension of ontological insecuritymechanisms, understood as the different ways that the ontological security of an agent can bethreatened, and the different types of existential anxieties that follow. To test and illustrate thistypology, the essay conducts an empirical case study of Russia’s engagement in the conflict inSyria since 2015. The results strongly indicate the presence of all ontological insecuritymechanisms, thus clearly implying that Russian behavior in Syria is driven by ontologicalsecurity concerns. The findings also demonstrate the typology’s usefulness and fruitfulness inmore closely specifying the nature of the ontological insecurity in particular cases.

This thesis considers whether donor countries that contribute with foreign aid to a recipientcountry also contribute with peacekeeping troops. The question is premised on the idea thatforeign aid serves as a proxy for national interest. Employing rigorous regression analysis witha high-dimensional fixed effects linear estimator, the study analyses a comprehensive datasetof country dyads that covers 30 year (1990-2019) and comprises 157 donor/origin countriesand 43 recipient/destination countries. I find a positive and significant relationship betweenforeign aid and troop, indicating that that sending foreign aid to a country is positivelyassociated with an increase in sending peacekeeping troops to that country.

Approved for public release, distribution is unlimited / American military relations with the Chinese People's Liberation Army (PLA) have been in a constant state of flux since their rocky beginnings during the Second World War. Since the Tiananmen Square incident of June 1989, efforts to reestablish a positive working relationship between the U.S. Department of Defense and the PLA have been restrained by domestic political pressures within both polities and a number of crises which increased political tensions between both nations' governments. Due to reactive policies implemented by both governments, engagement programs between the United States and PRC have yielded few tangible benefits to either side in the past fifteen years. This thesis addresses the history of U.S. military engagement with the PRC and discusses past American policies of "containment" and "engagement" of China. Case studies concerning American engagement with Taiwan and Thailand reveal the benefits of close links with partners in Asia and provide programs for possible emulation in the U.S.-PRC relationship. Through managed engagement programs such as systematic security summits, educational exchanges and partnership operations initiatives, a stable defense dialogue between American and Chinese militaries can yield significant results in reducing tensions between their two governments and averting future crises through improved communication and cooperation. / Major (Select), United States Air Force