War is the method adopted, when less violent means of persuasion have failed, to force your enemy to comply with your demands. There are three principal ways of effecting this--invasion of his country, raids on his territory, destruction or serious damage of his sea-borne commerce. Successful invasion must compel the invaded to come to terms, or his national existence will be lost. Raids upon his territory may possibly so distress him that he would rather concede your terms than continue the struggle.[90] Damage to his sea-borne commerce may be carried so far that he will be ruined if he does not give in. So much for one side of the account; we have to examine the other. Against invasion, raids, or attempts at commerce-destruction there must be some form of defence, and, as a matter of historical fact, defence against each has been repeatedly successful. If we need instances we have only to peruse the history of the British Empire. [Footnote 90: Though raids rarely, if ever, decide a war, they may cause inconvenience or local distress, and an enemy desiring to make them should be obstructed as much as possible.] How was it that--whilst we landed invading armies in many hostile countries, seized many portions of hostile territory, and drove more than one enemy's commerce from the sea--our own country has been free from successful invasion for more than eight centuries, few portions of our territory have been taken from us even temporarily, and our commerce has increased throughout protracted maritime wars? To this there can only be one answer, viz. that the arrangements for defence were effectual. What, then, were these arrangements? They were comprised in the provision of a powerful, well-distributed, well-handled navy, and of a mobile army of suitable strength. It is to be observed that each element possessed the characteristic of mobility. We have to deal here more especially with the naval element, and we must study the manner in which it operates.