Why do some democracies revert to non-democratic forms of governance? We develop an explanation of democratic reversals that emphasizes the influence of states’ external border relations on domestic politics. Latent threats to a state’s territory encourage political centralization of authority in the executive to defend against danger to the homeland. Latent territorial threat also facilitates the construction and maintenance of large land armies to fight threatening neighbors. Combined, latent territorial threat increases leaders’ domestic power, weakens democratic institutions, encourages other conditions threatening democratic survival, and, ultimately, leads to democratic reversals. Synthesizing prior research on territorial conflict, we generate a quantitative, continuous measure of latent territorial threat against all democracies with contiguous neighbors from 1946 to 2016, using Bayesian estimation. Empirical tests accounting for measurement uncertainty and other common determinants of reversals as well as brief reviews of individual cases of reversal provide robust evidence that democracy failed at higher rates in countries facing high levels of threats to their territory from neighbors. Our study implies that a complete account of the development of democratic institutions should emphasize that domestic factors alone fall short of explaining why democracies fail.

为什么一些民主国家会恢复到非民主的治理形式？我们对民主逆转进行了解释，强调国家的外部边界关系对国内政治的影响。对一个国家领土的潜在威胁鼓励行政权力的政治集中化，以抵御对祖国的威胁。潜在的领土威胁还促进了大型陆军的建设和维护，以对抗威胁邻国。联合起来的潜在领土威胁增加了领导人的国内权力，削弱了民主制度，鼓励了威胁民主生存的其他条件，并最终导致民主逆转。综合先前关于领土冲突的研究，我们生成了一个定量的、使用贝叶斯估计，连续测量 1946 年至 2016 年对所有相邻邻国的潜在领土威胁。考虑测量不确定性和其他常见逆转决定因素的实证检验以及对个别逆转案例的简要回顾提供了强有力的证据，证明民主在面临邻国对其领土的高度威胁的国家中失败率更高。我们的研究表明，对民主制度发展的完整说明应该强调仅靠国内因素并不能解释民主失败的原因。考虑测量不确定性和其他常见逆转决定因素的实证检验以及对个别逆转案例的简要回顾提供了强有力的证据，证明民主在面临邻国对其领土的高度威胁的国家中失败率更高。我们的研究表明，对民主制度发展的完整说明应该强调仅靠国内因素并不能解释民主失败的原因。考虑测量不确定性和其他常见逆转决定因素的实证检验以及对个别逆转案例的简要回顾提供了强有力的证据，证明民主在面临邻国对其领土的高度威胁的国家中失败率更高。我们的研究表明，对民主制度发展的完整说明应该强调仅靠国内因素并不能解释民主失败的原因。