This article traces resistance among members of the armed forces who opposed the military dictatorship in Brazil during the first four years of the regime, 1964–67. I show that despite scholars’ efforts to depict the 1964 coup as a project supported by the armed forces as a strategic and ideological unit, there were battle lines within those forces along which hard-liners and moderate interventionists battled for government control. There were, in fact, hundreds of officers and soldiers who opposed the coup and organized against it. To contain resistance efforts inside the armed forces, the generals who orchestrated the coup labeled opponents to intervention as communists and expelled them from the institution, in many cases under considerable duress. This article discusses the first opposition efforts of officers and soldiers, particularly the Nationalist Armed Resistance (RAN) and the Caparaó Guerrilla Movement. Members of the military who were opposed to the coup shared an anti-interventionism and nationalism that united them against the regime. After 1964, their efforts to oppose military interventionism, previously carried out inside the military barracks, became the fight of all its opponents, members of the armed forces and civilians alike.