The international system of the twenty-first century calls for new ways to resolve conflicts. Traditional influence strategies, such as deterrence and compellence, have undergone new revisions to conform to new challenges. A third strategy, reassurance, has demonstrated its potential in recent interstate conflicts after rarely being used during the Cold War. A strategy of reassurance involves one state's actions to increase the security of an adversary by helping the adversary in an issue that the adversary deems important. If the actions convince the adversary that the reassurer seeks peace, and the adversary also seeks peace, then the adversary reciprocates by sending an equally reassuring signal, completing an exchange that may lead to cooperation. This thesis analyzes the process of reassurance, using four modern case studies. In two of these case studies, one state's signal of reassurance was reciprocated, leading to a reduction in tensions. In the other two, the signal of reassurance was not reciprocated, leading to further tensions. This thesis seeks to find which conditions surrounded the successful cases. It will reveal that when benign intentions are made transparent through rhetoric, and when signals are perceived as costly, an adversary is more likely to reciprocate signals of reassurance.