Field Marshal Alexander Leslie was the highest ranking commander from the British Isles to serve in the Thirty Years' War. Though Leslie's life provides the thread that runs through this work, the authors use his story to explore the impacts of the Thirty Years' War, the British Civil Wars and the age of Military Revolution. Based on research from archival material from across Europe, Murdoch and Grosjean are able to explore how Leslie and his fellow officers brought a unique set of cultural and societal factors to the European theatre of war. Their new level of professionalism, learned on the battlefields of central Europe, is set alongside their close kin networks and cultural loyalty both on and off the battlefield.