Defensive Weapons and Defensive Alliances
研究防御性武器对和平的影响，发现单方面部署防御性武器在完全信息下会破坏稳定，但在战略风险下若对突袭防御效果远优于公开战争则可促进和平；防御性联盟则明确有利于和平。
We examine the effects of defensive weapons and their interaction with preemption. In a complete information setting, where attacks only occur as a consequence of predatory incentives, a unilateral acquisition of defensive weapons always destabilizes. Under strategic risk, where players might launch preemptive strikes, defensive weapons can help sustain peace. However, this only happens when such defensive systems are much more effective against a sneak attack than in an open war. Otherwise, defensive weapons are likely to also be destabilizing. We contrast these results with the effect of signing defensive alliances, which unambiguously bolsters the prospects of peace in both strategic settings.