Does the regime type of a foreign intervener influence the duration of civil wars? Existing research has shown that third-party support affects the outcome of a conflict. Moreover, studies show that the type of support offered to conflict actors can determine how a war ends. While this research has offered significant implications on conflict dynamics, extant works have overlooked the importance of characteristics of foreign supporters and how their attributes can impact conflict outcomes. Focusing on foreign troop support and quantities, this article examines the relationship between the regime type of a foreign supporter and the outcome of an armed conflict. We argue that regime type of an external troop sponsor can influence war duration based on two dynamics: selection effects and signaling effects. Specifically, troop assistance provided to warring parties by democracies decreases the length of civil wars and increases the likelihood for a one-sided victory for the supported faction. The empirical findings for all intrastate conflicts during the period 1975–2012 provide evidence for our claims that the regime type of an external intervener influences the outcome of a conflict.

外国干预者的政权类型是否会影响内战的持续时间？现有研究表明，第三方支持会影响冲突的结果。此外，研究表明，向冲突参与者提供的支持类型可以确定战争的结束方式。尽管这项研究对冲突的发展产生了重大的影响，但现有的研究却忽略了外国支持者的特征及其重要性如何影响冲突结果的重要性。本文着眼于外国部队的支持和数量，研究了外国支持者的政权类型与武装冲突结果之间的关系。我们认为，外部部队赞助者的政权类型可以基于两个动力学因素影响战争持续时间：选择效应和信号传导效应。具体来说，民主国家向交战各方提供的部队援助减少了内战的时间，并增加了被支持派系单方面获胜的可能性。1975年至2012年期间所有州内冲突的经验发现为我们的主张提供了证据，即外部干预者的政权类型会影响冲突的结果。