This project was developed within a PhD scholarship with the funding reference SFRH/BD/140378/2018.   With the beginning of the Spanish civil war and the communist threat that hung over the Iberian Peninsula the New State felt the need to create an institution that could combat this threat. In this sense, the Portuguese Legion was created on 30 September 1936. The Portuguese Legion played an important role within the authoritarian Portuguese regime, especially with regard to the Civil Defence Of The Territory during World War II, as well as for its preventive and surveillance action – carried out in particular by its Intelligence Service, internal structures such as the Formação Automóvel de Choque (F.A.C.) or Grupo de Intervenção Imediata (G.I.I.), and through collaboration with other civil organizations such as nationalist student organizations - of elements antagonistic to the regime. The aim of this work is to study the domestic counter-subversion implemented by the New State through the Portuguese Legion in articulation with the other control and repression organs (Political Police) and with sectors of civil society (Radical Right). Keywords: Portuguese Legion; Counter-subversion; New state; Political police; Radical right.