and bring as large a proportion as possible to bear on the decisive point. Obviously also one side may have an advantage over the other derived from geography; for instance, one may have, while the other has not, a great fortress near the common frontier, which will serve as a starting point for invasion. A general has to take the facts as he finds them, and make the best of them. He is the most skilful strategist who gains the most without fighting, and who succeeds in shifting the balance most largely in his own favour before engaging in decisive battle. Changes in tactics again are matters of great interest from age to age, not merely in themselves, but in connection with other developments on which at first sight they seem to have no bearing. Primarily they are matters of intellectual progress: the invention of gunpowder was an event of incalculable importance in human history. Similarly the material progress exemplified in making good roads brought with it the possibility of supplying an army in the field, instead of its being compelled to subsist on the country; and the possibility of doing this presently became a virtual necessity, because the best supplied army had a visible advantage. Thus gradually, through the progress of civilisation, armies have become highly elaborate machines, which require to be continuously supplied with food, ammunition, clothing, all the material without which they cannot act effectually. Hence they need to keep up continuous communication with their base of operations: and the conditions of strategy have been proportionally altered and rendered more complicated. There are other changes in tactics, that is to say in equipment and mode of fighting, which may be called political: and it is not always easy to see whether they are the causes, or the effects, of social and political changes; possibly they are both. In the early middle ages, the feudal aristocracy was dominant politically, the mailed knights were preponderant on the battle-field. When infantry had learned on the continent of Europe to repel mailed cavalry with the pike, in England to destroy them with the clothyard arrow, the political supremacy of the feudal nobles waned along with their military superiority: their overthrow was consummated when the development of artillery placed feudal castles at the mercy of the crown. Inasmuch as political power must in the last resort depend on physical force, it is plain that the nature of the armed strength of a nation at any time will be an important element in determining the nature of its government.