International Relations (IR) scholars, particularly those working in the rationalist tradition, argue that costly signalling is one of the main tools that policymakers have to resolve interstate bargaining disputes and, ultimately, to minimize the occurrence of war. Recent rationalist work has greatly advanced our understanding of how costly signalling works in global politics, particularly by unpacking how militarized escalations can signal potential antagonists (e.g. Slantchev 2011). But the current literature is too hasty in dismissing the importance of non-militarized signalling during international crises, particularly for leaders worried about the risk of accidental wars. This paper presents mandatory evacuations (MEs) as a form of non-militarized escalation that states have been increasingly using since World War II to credibly signal their opponents. We illustrate our claims with a case study of China’s preparations for the 1979 Sino-Vietnamese War, when it ordered a massive evacuation along its northern border as a costly signal towards the Soviets.