Existing studies on Foreign Nuclear Deployment (FND)—the practice of nuclear powers stationing nuclear weapons on the territory of another state—have primarily focused on extended deterrence and nonproliferation. However, the effects of FND on the...
Existing studies on Foreign Nuclear Deployment (FND)—the practice of nuclear powers stationing nuclear weapons on the territory of another state—have primarily focused on extended deterrence and nonproliferation. However, the effects of FND on the conflict behavior and defense spending of host states remain underexplored, with prior analyses limited to fragmented case studies lacking generalizability. This study addresses these gaps by systematically examining the behavioral changes of host states under FND through a comprehensive, multi-dimensional approach.
The findings demonstrate that FND influences host states' conflict behavior. States hosting foreign nuclear deployment—hereafter nuclear clients—tend to adopt more uncompromising positions in diplomatic disputes with rival states over territorial issues. This shift is driven by both a perceived enhancement of their material capabilities and increased confidence in the security guarantees provided by their nuclear patron. With a strengthened sense of security, nuclear clients exhibit bolder behavior in diplomatic conflicts. Conversely, in military conflicts involving the actual mobilization of forces, FND has the opposite effect, making nuclear clients more restrained. The effects of foreign nuclear deployments vary depending on the level and type of conflict. In line with the logic of the stability–instability paradox, in conflicts with a high risk of escalation into nuclear war, nuclear protégé states tend to exercise restraint in their conflict behavior. In contrast, when the risk of such escalation is low, they may act more aggressively. Additionally, these nonlinear effects may stem from the nuclear patron’s diplomatic interventions, motivated by a desire to avoid entanglement in unwanted military conflicts.
In addition, the study finds that FND tends to suppress defense spending in nuclear clients, though this effect is not universal. It is most prominent among clients hosting U.S. nuclear deployments, where a noticeable decline in defense spending occurs immediately after deployment. Moreover, this suppressive effect often persists for some time following the withdrawal of nuclear weapons.
The study employs both quantitative and qualitative methods. It uses datasets on FND and conflict behavior to conduct a probit regression analysis, assessing the effects of FND on conflict behavior. Subsequently, it analyzes the relationship between FND and defense spending through linear regression using panel data. Complementing these quantitative analyses, a qualitative case study examines how U.S. nuclear deployments affected Taiwan’s conflict behavior and defense spending, drawing from relevant literature.
The results confirm that FND exerts differentiated effects depending on the level and type of conflict. Additionally, FND is shown to partially suppress defense spending in nuclear clients. The case study further suggests that the nuclear patron’s desire to avoid direct military entanglement is likely a key factor shaping these behavioral shifts. It also provides concrete evidence of the suppressive effect on defense spending in actual cases.