Conflict between civilizations will be the latest phase in the evolution of conflict in the modern world. For a century and a half after the emergence of the modern international system with the Peace of Westphalia, the conflicts of the Western world were largely among princes-emperors, absolute monarchs and constitutional monarchs attempting to expand their bureaucracies, their armies, their mercantilist economic strength and, most important, the territory they ruled. In the process they created nation states, and beginning with the French Revolution the principal lines of conflict were between nations rather than princes. In 1793, as R. R. Palmer put it, "The wars of kings were over;
Williams enjoyed opera from an early age, particularly Mozart and Wagner . Patricia Williams writes that he attended performances of the Carl Rosa Company and Sadler's Wells as a teenager.  In an essay on Wagner, he described having been reduced to a "virtually uncontrollable state" during a performance by Jon Vickers as Tristan at Covent Garden .  He served on the board of the English National Opera from 1968 to 1986,  and wrote an entry, "The Nature of Opera," for The New Grove Dictionary of Opera .   A collection of his essays, On Opera , was published posthumously in 2006, edited by Patricia Williams.  
In 1927, he met and married Elizabeth (Betty) Carver, née Hobart, widow of Oswald Carver , Olympic rowing medallist who had been killed in the First World War.  Betty Carver was the sister of the future Second World War commander, Major General Sir Percy Hobart .  Betty Carver had two sons in their early teens, John and Dick, from her first marriage. Dick Carver later wrote that it had been "a very brave thing" for Montgomery to take on a widow with two children.  Montgomery's son, David , was born in August 1928. 
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