This project examines how deterrence operates in informal security relationships where commitments remain ambiguous. It develops a theory of challenger inference, arguing that deterrence outcomes depend not primarily on formal assurances or signalling credibility, but on how challengers interpret great-power intervention thresholds under uncertainty. Focusing on cases such as US–Ukraine and US–Taiwan, the study combines formal modelling with qualitative process tracing to explain why challengers often escalate incrementally rather than decisively despite the risk of external intervention.

This project examines how middle powers adjust their alignment strategies within asymmetric security hierarchies. It argues that variation in hedging and alignment emerges from how states infer a patron’s tolerance threshold for strategic deviation, rather than from material constraints alone. By identifying a belief-based mechanism centred on threshold inference, the paper offers a new explanation for why middle powers move along the alignment–hedging spectrum under great-power rivalry.

This project examines how nuclear weapons reshape escalation dynamics during interstate crises. It argues that nuclear capability creates perceived escalation ceilings that alter how actors interpret threats and translate them into violence. By focusing on threshold uncertainty rather than deterrence success alone, the study explains why crises involving nuclear-armed states often exhibit calibrated, limited escalation rather than decisive confrontation.