When in the spring of the year 1913 my old College did me the honour to appoint me its first lecturer in Military History, I was obliged for the first time to ask myself seriously, What is military history? I confess that I have found it very difficult to furnish a satisfactory answer. Some would reply with a light heart that military history is the history of wars and warring. But what, in its turn, is war? It has been defined as an instrument of policy for the imposition of the will of one community upon another by force of arms. The definition is not a bad one. But _force of arms_ is a very vague term, and must not be taken necessarily to imply an _armed force_ in the ordinary acceptation of the words. You will remember that after the French fleet had been swept by us from the seas in 1805, Napoleon, unable to attack England by any other means, decreed the exclusion of British manufactures from the Continent, and endeavoured to ruin her by shutting her out of her markets. This he was able to do because his previous conquests had placed the control of many of the principal ports on the Continent in his hands. But though he strove thus to inflict his will upon England by might of arms, the armed men necessary for enforcing it were nothing more formidable than a small body of Custom-house officers. No doubt these functionaries, or some of them, carried weapons and in case of need were prepared to use them; but they cannot be considered as a military body. None the less as an act of war the Continental System was a bitter and deadly stroke, which nearly proved successful. Is the history of the Continental System, therefore, military history? So far as concerns the invasion of Spain, Portugal and Russia to coerce those countries into the acceptance of it, undoubtedly it is. But as regards England, the power at which it was really aimed, what are we to say of it? How did we endeavour to combat it? How does any country invariably combat the commercial restrictions of any other? First by imposing retaliatory restrictions of her own, or engaging in a war of blockades or tariffs, which may be called regular commercial warfare; secondly, by the practice of smuggling, which may be called irregular commercial warfare. Is the history of a war of tariffs, then, military history? If we answer in the affirmative there is no escape from the logical conclusion that the never-ceasing contest between smugglers and revenue-officers in all countries is military history. Moreover, since revenue-officers are only departmental police, it follows that the external struggle between the breakers and the upholders of the law at large--between criminals and the police--is also military history. But this is to say that the history of social communities generally is military history; and I cannot think this to have been in the mind of the generous founder of the lecturership which I have the honour to hold.