Many of our theories in political science about the nature of international conflict and the threats to democratic development make assumptions about the importance of individual-level attitudes under conditions of external threat. Citizens that feel that sense of salient threat from outside the state's borders react in ways that lead to centralized states, autocracies, and even conflict between states. This conforms well with what we know from international relations research, as well as political behavior research. However, much of our analyses do not fully test these arguments. In international relations, individual-level attitudes are usually assumptions of broader arguments of development and conflict, for which the assumptions are affirmed in the outcomes that individual-level attitudes are purported to explain. Political behavior research is more interested in the role of asymmetrical, or normative'', threats that lead to a divergence of attitudes in society, and not the convergence of opinion that affect state development processes inside states and conflict processes between states. International relations scholarship and political behavior research overlap in important ways, but still have much to learn from each other. This dissertation fully incorporates international relations theories and political behavior scholarship through an assessment of how salient, external threats to the state affect individual-level political attitudes. Identifying territorial threats as a class of salient external threats, ex ante, I argue and demonstrate the effect these threats have on three distinct, though related, individual-level attitudes. First, I show how territorial threat leads individuals to prefer strong state leaders, with few bounds on discretionary power. These threats routinely coincide with the emergence of state leaders, though the argument I advance is these threats lead individuals to $prefer$ this type of leader. Second, I show the multifaceted effect of territorial disputes on individual-level subjective well-being, the so-called ultimate dependent variable in social science.'' I find that citizens living under constant threat are unsurprisingly unhappy in general, which, I argue, is part of the conflict process linking crises over territory and war. However, citizens living in states that initiate a lot of territorial threats are happier in general, which follows because the disputed territory is a type of coveted good that the leader tries to provide to important regime supporters. Finally, I demonstrate the unique effect that territorial threat has on individual-level tolerance of corruption. Citizens living under territorial threat will tolerate government corruption, provided the government is working toward the security of the territory. However, citizens are unlikely to afford this same liberty to their fellow citizens. Under conditions of territorial threat, societal corruption is seen as undermining group norms. Taken together, these analyses bridge the gulf between international relations research and political behavior research, also demonstrating the unique importance of territorial issues for our understanding of politics in the international system.