Chapter 5 considers evidence that disagreements about the jus ad bellum are linked to disagreements about between ‘pacificist’ and ‘interventionist’ strategic cultures ‘extra-legal’ politico-strategic and ethical principles. The chapter describes extra-legal reasoning, particularly in evaluating facts, in UK government statements and writings by eight legal scholars about the lawfulness of military action in Kosovo (1999), Afghanistan (2001) and Iraq (2003), judges’ opinions in the ICJ cases Nicaragua (1986), Wall (2004), and Congo (2005), and in interviews and a survey with thirty-one UK-based international lawyers. The chapter concludes that lawyers’ extra-legal reasoning and views on lawfulness of force broadly align, on a continuum between pacificists preferring a restrictive jus ad bellum, and interventionists favouring an expansionist approach. But again, there are caveats. Most interventionists accept some legal prohibitions they believe are politically or ethically wrong. Most pacificists accept some justifications they politically or ethically condemn. This suggests most lawyers’ politico-strategic and ethical intuitions act as forms of cognitive biases, shaping but not wholly determining opinions about legal interpretation and the jus ad bellum.