After 1911 it must have been obvious to most people who considered the matter carefully that in certain events the Triple Entente would become an alliance. It is the interest as well as the duty of allies to stand by one another from first to last, and act together in the manner most likely to result in victory for the alliance. What then was the manner of co-operation most likely to result in victory for that alliance which lay dormant under the Triple Entente? But first of all, to clear away one obscurity--_Invasion_ was not our problem; _Defence_ was our problem; for the greater included the less. The word 'defence' is apt to carry different meanings to different minds. The best defence of England and British interests, at any given time, may or may not consist in keeping our main army in the United Kingdom and waiting to be attacked here. It all depends upon the special circumstances {250} of each case. The final decision must be governed by one consideration, and one only--how to strike the speediest, heaviest, and most disabling blow at the aggressor. If by keeping our army in England and endeavouring to lure the enemy into our toils, that end is most likely to be accomplished, then it is obviously best to keep our army here. If by sending it into the north of France to combine with the French the supreme military object has a superior chance of being achieved, then it is best to send it into the north of France. A defensive war cannot be defined and circumscribed as a war to drive out invaders, or even to prevent the landing of invaders. The best way to defend your castle may be to man the walls, to fall upon the enemy at the ford, to harry his lands, or even to attack him in his castle. There is no fixed rule. The circumstances in each case make the rule. [Sidenote: CO-OPERATION WITH FRANCE] A war is not less a defensive war if you strike at your enemy in his own territory, or if you come to the aid of your ally, whose territory has been invaded or is threatened. In the circumstances which prevailed for a considerable number of years prior to the outbreak of the present war, it gradually became more and more obvious, that our soundest defence would be joint action with France upon her north-eastern frontier. For there, beyond any doubt, would Germany's supreme effort be made against the Triple Entente. If the attack failed at that point, it would be the heaviest and most disabling blow which our enemy could suffer. If, on the other hand, it succeeded, France and England would have to continue the struggle on terms immensely less favourable. {251}