If, then, we only regard war between contiguous continental States, in which the object is the conquest of territory on either of their frontiers, we get no real generic difference between limited and unlimited war. The line between them is in any case too shadowy or unstable to give a classification of any solidity. It is a difference of degree rather than of kind. If, on the other hand, we extend our view to wars between worldwide empires, the distinction at once becomes organic. Possessions which lie oversea or at the extremities of vast areas of imperfectly settled territory are in an entirely different category from those limited objects which Clausewitz contemplated. History shows that they can never have the political importance of objects which are organically part of the European system, and it shows further that they can be isolated by naval action sufficiently to set up the conditions of true limited war. Jomini approaches the point, but without clearly detaching it. In his chapter "On Great Invasions and Distant Expeditions," he points out how unsafe it is to take the conditions of war between contiguous States and apply them crudely to cases where the belligerents are separated by large areas of land or sea. He hovers round the sea factor, feeling how great a difference it makes, but without getting close to the real distinction. His conception of the inter-action of fleets and armies never rises above their actual co-operation in touch one with the other in a distant theatre. He has in mind the assistance which the British fleet afforded Wellington in the Peninsula, and Napoleon's dreams of Asiatic conquest, pronouncing such distant invasions as impossible in modern times except perhaps in combination with a powerful fleet that could provide the army of invasion with successive advanced bases. Of the paramount value of the fleet's isolating and preventive functions he gives no hint. Even when he deals with oversea expeditions, as he does at some length, his grip of the point is no closer. It is indeed significant of how entirely continental thought had failed to penetrate the subject that in devoting over thirty pages to an enumeration of the principles of oversea expeditions, he, like Clausewitz, does not so much as mention the conquest of Canada; and yet it is the leading case of a weak military Power succeeding by the use of the limited form of war in forcing its will upon a strong one, and succeeding because it was able by naval action to secure its home defence and isolate the territorial object.