Shocked by the horrors of the Great War he saw as an ambulance driver just behind the front lines, Trevelyan became more appreciative of conservatism as a positive force, and less insistent that progress was inevitable. In "History of England" (1926), he searched for the deepest meaning of English history. Cannadine says he reported they were "the nation's evolution and identity: parliamentary government, the rule of law, religious toleration, freedom from continental interference or involvement, and a global horizon of maritime supremacy and imperial expansion".