Einstein once refused to speculate on the types of weapons to be used in a hypothetical third world war; but he was succinct and specific in naming those of an ensuing fourth global contest – “rocks”. Just as nuclear arms have very possibly made World War II the penultimate great conflict, the super bombs have created a climate in which international rivalries contend through cold war confrontation, police actions and limited warfare. The total terror of our nuclear age has thus far served to confine military clashes to the battlefields of Korea, Vietnam and the Near East, all restricted arenas in comparison to those of 1914–18 and 1939–45. Fear of thermonuclear retaliation has prevented attacks on, to use MacArthur's term, the “privileged sanctuaries” of our era's prime combatants.