This thesis examines the Irish amateur military tradition in the British Army from 1854 until 1945, as separate to the amateur military tradition in Great Britain. The work argues that such a difference did exist but, also, within this, two further traditions emerged. Firstly, the re-emergence of the Protestant volunteering tradition, witnessed in Ulster as early as the seventeenth century, and, secondly, a Catholic amateur military tradition largely present in the Irish militia. Importantly, these two traditions, although not directly competing, also reflected Irish, and later Northern Irish, society up until the end of the Second World War. It will assess these traditions by looking at a variety of different aspects: the political and strategic considerations of the use of Irish auxiliaries at a time when there was a degree of upheaval in Ireland; the officer corps of the amateur forces, and how this developed over time; likewise, for the rank and file, its changing nature is evaluated; the discipline and morale of these forces is assessed, with special attention given to how religious composition affected this; their use on active service is considered; and, finally, the contemporary image, both inside and outside of Ireland is considered in order to build a picture of the auxiliary forces cultural impact on society as a whole. In' essence, this approach has previously been used to assess the British Army as a whole, especially during the Victorian and Edwardian periods, and also the amateur forces of Great Britain. However, this work builds upon this concept to evaluate the Irish position in detail, within the British context, for the first time. In so doing, the thesis also disproves some of the assumptions made about the Irish position and how its amateur forces were placed within its unique political, social, and cultural environment.