During the first three years of the Vietnam War, the United States made over 2000 attempts to open negotiations with the North Vietnamese. North Vietnam ignored or denied all of these overtures to open talks. By April 1968, following repeated rebuffs, Hanoi changed its position after President Johnson announced that the U.S. would halt bombing above the 20th parallel. What explains Hanoi’s initial firm position against talks and the sudden policy change in 1968? What are the drivers behind a state’s willingness to talk with the enemy while fighting, what considerations do leaders account for when deciding when and how peace talks can begin, and why do some states reject or ignore overtures to come to the negotiating table?

In a new Journal of Theoretical Politics article, FSI Center Fellow Oriana Skylar Mastro and Duke University’s political scientist David Siegel advance a new theory of wartime diplomacy to answer these questions. Using a formal model, they find that states are inclined to initiate negotiations when two conditions are met: firstly, when their adversaries perceive escalation as excessively costly, and secondly, when there is an indication of exceptional resilience that only those possessing high resilience value. To shed light on the dynamics of the second condition, Mastro and Siegel present an in-depth case study examining the evolving negotiation approach of North Vietnam throughout the Vietnam War.

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The second condition arises when the opponent does not view escalation as overly costly and when the likelihood of successful escalation is hard to assess, but there is a signal of high resilience that helps identify resilient entities. “States will choose typically open stances, potentially inviting escalation, only when they have demonstrated enough resilience to mitigate the escalation risk,” write Mastro and Siegel. This dynamics explains why North Vietnam’s diplomatic posture changed during the second phase of the Vietnam War.

Early on in the war, both the United States and North Vietnam believed that a willingness to talk would convey weakness. North Vietnam needed to sense hesitancy in U.S. confidence in the effectiveness of escalation before opening to negotiations. In 1968, the Tet Offensive allowed North Vietnam to demonstrate its resilience and constrain U.S. strategic capacity by inflicting casualties and steadily depleting its resources.

Even though North Vietnam was materially weaker and Tet failed by all operational measures, it represented a psychological shock to U.S. leadership and “finally convinced the U.S. of Hanoi’s resilience, reducing the likelihood that an open diplomatic posture would be interpreted as weakness.” North Vietnam had been reluctant to negotiate before it could adequately signal its resilience, maintaining a closed diplomatic posture for three years. But after Tet, having communicated its resilience to Washington, Hanoi “no longer viewed an open diplomatic posture as a liability in the war effort.”

The authors’ findings suggest that states are concerned about the negative material consequences that their diplomatic approach might have on the enemy. Thus, face-saving measures from the adversary are limited because the enemy would still perceive an open stance as a sign of weakness, potentially leading to further escalation. These findings are significant, as they demonstrate how counterproductive attempts to coerce opponents to negotiate can be.

At the same time, the study highlights new opportunities for external mediators “who can provide guarantees in ways that lessen the strategic costs of conversation,” Mastro and Siegel argue.