On Tuesday, December 3, 1940, Winston Churchill read a memorandum by the military strategist Basil Liddell Hart that advocated making peace with Nazi Germany. It argued, in a summary written by Churchill’s private secretary, Jock Colville, that otherwise Britain would soon see “Western Europe racked by warfare and economic hardship; the legacy of centuries, in art and culture, swept away; the health of the nation dangerously impaired by malnutrition, nervous strains and epidemics; Russia . . . profiting from our exhaustion.” Colville admitted it was “a terrible glimpse of the future,” but nonetheless courageously concluded that “we should be wrong...