The only choice is both choices: balancing assurance and coercion in nonproliferation-focused alliance-management strategies

ABSTRACT

Conventional theories of alliance management often overemphasize the utility of either assurance or coercion in preventing allied nuclear proliferation. Historical analysis reveals that prioritizing either of these two tactics to the exclusion of the other is inadvisable. A strategy that focuses solely on security guarantees or coercive threats is likely to encourage an allied state to pursue a hedging strategy, in which the client state continues to clandestinely develop its own nuclear capabilities while remaining underneath its patron’s defensive “umbrella.” This article introduces a new framework for understanding the effectiveness of nonproliferation-focused alliance-management strategies. By exploring the cases of West Germany and South Korea, the article concludes that the best way to prevent allies from pursuing nuclear weapons is to combine assurance with coercion. This establishes an incentive–punishment relationship that limits an ally’s motivation to develop nuclear weapons. These conclusions have particular salience today, as conversations over nuclear-weapons development have become increasingly normalized in Germany and particularly in South Korea. The United States’s capacity to influence its allies’ nuclear behavior is currently being eroded through the degradation of both patron credibility and client dependence, weakening the long-term viability of the global nonproliferation regime.