Alfred T. Mahan Analyses the Influence of Sea Power on International Politics
More almost than armies, which in these changes [in territory among European nations] were the instruments of forcible yet beneficent adjustments, navies are instruments of international relations. They are so more purely, because a navy, as has long been recognized, can very rarely be used to oppress the people of its country in their domestic conditions, as armies often have been. While thus more strictly international, the scope of navies is also far wider. They can be felt where the national armies cannot go, except under naval protection. Just here it becomes necessary to point out a further distinction, which closely affects the United States and shows more clearly how entirely the navy, and consequently the numbers and constitution of the navy, is a matter to be determined by international considerations, and not merely by those which are domestic and internal to the country. Exactly as a navy cannot be used as an instrument of domestic oppression, so in international affairs it is less effective for aggression than armies are; yet to a state whose frontiers are maritime, and to the external interests of such a state, it is more effective as a defensive force for protection, because of its mobility. The United States has neither the tradition nor the design to act aggressively beyond seas, but she has very important transmarine interests which need protection, as well as two home coasts separated by a great intervening space and open to attack.
The question for the United States, as regards the size of its navy, is not so much what it desires to accomplish as what it is willing or not willing to concede. For instance, we have shown plainly that we are unwilling to concede anything as regards the control of the Panama Canal, even to discuss the right to fortify it. The Monroe Doctrine, too, is only a claim to maintain security for that which we possess. In no sense does it propose to add to our holdings. How far is the country prepared to be obliged to concede on these points, because unready to maintain them by organized force?