While aspects of Halliday’s theory have been adopted for the study of ideology in discourse - in particular via Critical Discourse Analysis - these applications of his ideas have not attempted to bring the full weight of Halliday’s model to the problem of understanding the phenomenon and practical manifestation of ideology. A consideration of Halliday’s model reveals, first of all, that Halliday, like Vološinov in linguistics, and Mannheim in sociology, sees ideology as entirely pervasive. The act of analysing ideology is, therefore, ideological, a conundrum known as ‘Mannheim’s paradox’. This paradox, rather than hindering the study of ideology, invites the researcher to work explicitly with the concepts in one’s theoretical model, and to test their usefulness in producing robust and revealing descriptions of the ideologies that shape human experience and behaviour. This paper explores ideology in the context of the ‘architecture’ of human language, that is, with reference to key concepts in Halliday’s theory, including realisation/stratification, instantiation, register and context of situation and of culture. I argue that while ideology is permeable with respect to register - the same ideology can be expressed across a variety of contexts - the concepts of context and register are crucial to showing the affordances of particular registers to the dissemination of specific ideologies. I illustrate this claim by analysing one text with respect to its context of situation (drawing on Hasan’s context networks) and its context of culture. I consider how the text, as an instance of a particular register, is an ideal host for ideological meanings that legitimate organised violence in the pursuit of geopolitical power.