This article analyses the history of civil-military relations from the aftermath of the Napoleonic Wars until the demise of the New State. It shows that the attitude of the military in 1974 was not merely conjunctural and that the tendency to intervene in politics was entrenched in the armed forces since the fall of the ancien régime. Although the nature and intensity of its participation in state affairs evolved throughout the nineteenth and twentieth centuries, the Portuguese military never completely accepted civilian supremacy. Military interventionism was nurtured by political polarization, institutional weakness, and disagreements over foreign policy, the use of the armed forces against internal enemies and the deficient equipment and preparation of the troops. Periods of active involvement in politics alternated with others in which interventionism remained latent.