This paper investigates the role and significance of nationalist ideology and bureaucratic organisation in two quite different armed organisations that nonetheless shared certain key features. Both asserted their right to use force through nationalist ideology, claiming to be the legitimately-constituted army of a nation and state. Both were also organised like formal military bureaucracies with hierarchical command structures and institutions. Drawing on interviews with more than twenty ex-combatants from the VRS and the Provisional IRA this paper compares the role of nationalist ideology and of bureaucratic structures in these two organisations. We find that although both organisations are seen as being highly motivated by nationalist ideas, the picture is much more complex and nationalism is much less present than expected. Instead individualist motivations, small group solidarity and local networks dominate. We find too that, contrary to expectations, bureaucratic systems were more rigidly formalised in the more clandestine group, the IRA.