GEORGE CLARK. War and Society in the Seventeenth Century. (The Wiles Lec tures Given at the Queen's University, Belfast, 1956.) Pp. vii, 156. Cambridge: Cambridge University Press, 1958. $3.50. ROBERT S. QUIMBY. The Background of Napoleonic Warfare: The Theory of Military Tactics in Eighteenth-Century France. (Columbia Studies in the Social Sciences, No. 596.) Pp. viii, 385. New York: Columbia University Press, 1957. $6.75