This article explores the writings of Hugo Grotius on the law of civil war. First, the article takes a look at what Grotius wrote about the Dutch revolt, the civil war during which he himself lived and which he helped to legitimise. Second, the article notes how in legal practice the Dutch revolt also provided a valuable early precedent for the later scholars of the law of civil war, who were more concerned with questions of revolutionary prize jurisdiction and the problem of recognition. Third, the article explores the elements relating to these questions of civil war in Grotius’s volitional law of nations as presented in De iure belli ac pacis. These provided Grotius’s most enduring legacy for the later scholars on the law of civil war.