It is widely believed that “petrostates,” or countries whose economies rely heavily on oil exports, are at greater risk from external aggression. This popular view has made frequent recourse to the neo-Malthusian intuition that, in a world of material scarcity, resource predation will be rampant. Recent empirical research, however, has shown that petrostates are neither more common targets of military attack nor particularly peaceful members of the international community. In fact, available statistical analyses overwhelmingly suggest that, in terms of conflict initiation, these states are mostly on the offensive in world politics—a phenomenon often referred to as “petroagression.” Despite this finding, little is known about what accounts for variation in petrostate belligerence. Not all petrostates are international troublemakers, and their propensity to threaten or use military force has varied both across geography and over time. This dissertation attempts to explain this within-group variation, using two conceptual experiments. The first heeds to the internal organization of petrostates, examining how differences in their regime institutions could mediate (strengthen or weaken) the conflict-inducing effects of oil income. It is argued that, because of certain compositional and identity characteristics of their ruling coalitions, petrostates with personalist institutions would be more potent conflict initiators than comparable oil exporters of nonpersonalist institutional makeup. The second conceptual experiment abstracts from petrostates’ internal attributes, exploring potential sources of variation in their external environments. Adopting a system–subsystem perspective, this analysis proposes that, all else equal, exogenous structural variables—in particular, superpower penetration in regional subsystems containing petrostates—could account for differences (spatial and temporal) in those states’ conflict behavior. Although the dissertation’s main thrust is theoretical, empirical evidence providing preliminary support for these variational propositions is also offered.