This is the first such study of Operation Banner, the British Army's campaign in Northern Ireland. Drawing upon extensive interviews with former soldiers, primary archival sources including unpublished diaries and unit log-books, this book closely examines soldiers' behaviour at the small infantry-unit level (Battalion downwards), including the leadership, cohesion and training that sustained, restrained and occasionally misdirected soldiers during the most violent period of the Troubles in Northern Ireland. It contends that there are aspects of wider scholarly literatures - including from sociology, anthropology, criminology, and psychology - that can throw new light on our understanding of the British Army in Northern Ireland. It also offers fresh insights and analysis of incidents involving the British Army during the early years of Operation Banner, including the 1972 'Pitchfork murders' of Michael Naan and Andrew Murray in County Fermanagh, and that of Warrenpoint hotel owner Edmund Woolsey in South Armagh. The central argument of this book is that British Army small infantry units enjoyed considerable autonomy during the early years of Operation Banner and could behave in a vengeful, highly aggressive or benign and conciliatory way as their local commanders saw fit. The strain of civil-military relations at a senior level was replicated operationally as soldiers came to resent the limitations of waging war in the UK. The unwillingness of the Army's senior leadership to thoroughly investigate and punish serious transgressions of standard operating procedures in Northern Ireland created uncertainty among soldiers over expected behaviour and desired outcomes. Overly aggressive groups of soldiers could also be mistaken for high-functioning units - with negative consequences for the Army's overall strategy in Northern Ireland.