This article focuses on how the Spanish Civil War was experienced and understood by those who in previous years had declared themselves pacifist or antimilitarist, mainly the pacifist movement around the War Resisters’ International (WRI) and the antimilitarist and anarchist trade union Confederación Nacional del Trabajo (CNT). In the article, I deal with the different ways in which these men and women analysed the reality of war, starting with the use of violence and the attitude towards the creation of an army, followed by the questions of recruitment and finishing with the ideological repression behind Republican lines. These perspectives will help us understand the militarization process that occurred on the Republican side, the way that the culture of war was experienced and the strategies that were sometimes carried out to prevent some of its negative consequences.