For more than twenty-five years, David Nott has taken unpaid leave from his job as a general and vascular surgeon with the NHS to volunteer in some of the world's most dangerous war zones. From Sarajevo under siege in 1993, to clandestine hospitals in rebel-held eastern Aleppo, he has carried out life-saving operations and field surgery in the most challenging conditions, and with none of the resources of a major London teaching hospital. The conflicts...