War is a mass phenomenon. To penetrate the basic causes of war, we must discern the factors which have made millions of people abandon their habitual modes of life, their occupations, and their moral concepts to participate in murder and destruction. We should therefore put greater stress upon the simple conscious and. subconscious impulses which rule the behavior of the masses.

p. 3 - Europe on the Move: War and Population Changes, 1917-1947, 1948