This book investigates, and explains, the extent to which different liberal democracies have resorted to the use of force since the 9/11 terrorist attacks. The responses of democratic states throughout the world to the September 2001 terrorist attacks have varied greatly. This book analyses the various factors that had an impact on decisions on the use of force by governments of liberal democratic states. It seeks to explain differences in the security policies and practices of Australia, Canada, France, Germany and the UK regarding the war in Afghanistan, domestic counterterrorism measures and the Iraq War. To this end, the book combines the concepts of strategic culture and securitisation into a theoretical model that disentangles the individual structural and agential causes of the use of force by the state and sequentially analyses the impact of each causal component on the other. It argues that the norms of a strategic culture shape securitisation processes of different expressions, which then bring about distinct modes of the use of force in individual security policy decisions. While governments can also deviate from the constraints of a strategic culture, this is likely to encounter a strong reaction from large parts of the population which in turn can lead to a long-term change in strategic culture. This book will be of much interest to students of strategic culture, securitisation, European politics, security studies and IR in general.