The revolutionary insurrection of October 1934 was a key event in the Spanish Second Republic. The process of “radicalisation” is frequently used to understand this event and this thesis re-evaluates how radicalism can be conceptualised, demonstrating that it was a historically contingent force and a dynamic and reactive process, resulting from a combination of factors and strategies. Rather than a narrow focus on labour reform, this thesis grounds radicalism in the social environment and communities of the coalfields, the practice of politics at local level and the struggles which emerged during the Republic. Local communities were more complex and divided than has frequently been portrayed, and this was crucial to the process of radicalisation. Radicalism and October 1934 cannot be understood without an appreciation of the particular political practice of the coalfields. Analysis of episodes of violence, boycotts and mobilisation over religious policy along with a re-evaluation of the role of the fascism enable us to understand what politics and the Republic meant in Asturias, and the dynamic process of radicalisation. The revolutionary insurrection of 1934 was an attempt to fashion a “revolutionary community”, which was formed in tension with previous experiences of community in the coalfield. The profound effects of repression on local communities were important for shaping the militant, radical, yet fragile, politics of the left in spring 1936. As such, this thesis, through an analysis of the everyday struggles and lived experience of the Second Republic, provides a complex and nuanced vision of both the coalfields and the wider Republic through an emphasis on the contingent nature of radicalism and changing idea of the Republic.