What thrust us into war were not Hitler's political teachings: the cause, this time, was his successful attempt to establish a new economy. The causes of the war were: envy, greed, and fear.
The Second World War, 1939-1945: a strategical and tactical history, (1948)
The War of the Roses in England and the Civil War in America were both intestinal conflicts arising out of similar ideas. In the first the clash was between feudalism and the new economic order; in the second, between an agricultural society and a new industrial one. Both led to similar ends; the first to the founding of the English nation, and the second to the founding of the American. Both were strangely interlinked; for it was men of the old military and not of the new economic mind—men, such as Sir Humphrey Gilbert and Sir Walter Raleigh — who founded the English colonies in America.
Grant and Lee: A Study in Personality and Generalship, ch. 1 (1957)