Rooted in the middle-ground approaches to securitization which oppose a reductive understanding of the process of threat construction as either 'discursive' or 'social, this thesis adopts a pragmatic approach that combines elements of both into a richer and empirically-useful model. Thus, it unpacks and refines some of key tenets of speech act theory, and combines them with insights from Bourdieusian social field theory. More concretely, this thesis proposes a return to the Austinian notion of the total speech act and explores the range of minimal and optimal effects of securitization. This more nuanced understanding of the process is explored through the prism of macrosecuritization with the use of discourse-historical analysis. The thesis also employs insights from field theory to look at actors and audiences relationally and dynamically, examining questions of capital formation, accumulation and transfer, and adopting a taxonomic approach to identifying actors. It also introduces the concept of spacetime, which showcases the relativity of time and space that permeates the objective and subjective (and virtual) worlds, and provides a three-dimensional understanding of macrosecuritization processes. It captures thus not just how the temporal and spatial dimensions shape securitization, but also how the construction of threats can accelerate or slow down time, and constrict or expand spaces. Empirically, this thesis contributes to the emerging literature on macrosecuritization through three case studies, covering the foreign policy, economic and security domains, and innovatively exploring the euro crisis through a macrosecuritizing framework.