THE change from mediaeval to modern methods in the art of war is closely related to the general transformation of European civilization which goes by the name of the Renaissance. The revival of interest in ancient history and literature had a distinct effect on military theory and practice. The new spirit of inquiry and experiment applied itself vigorously to military problems. Moreover the avowed national separatism which replaced the sham imperialism of the Middle Ages accentuated the rivalry between states and produced wars which were more frequent, more prolonged, more general, and more intense than those of the preceding centuries. The history of these wars, waged in an age of eager intellectual activity, reveals, as we should expect it to reveal, rapid progress, amounting almost to revolution, in the use of arms, but what makes an examination of the subject singularly instructive is the fact that the most important of these campaigns were fought in Italy during the culminating years of the Italian Renaissance. The finest minds of the day had the opportunity of witnessing, of recording, and of commenting on the exploits of the leading captains and the most famous troops of Europe. They assisted in the interplay of ideas and the comparison of experiences.  The fruit of this period of intensive cultivation of the art of war was the military science of the modern world.