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Sea power

Mahan believed that national greatness was inextricably associated with the sea, with its commercial use in peace and its control in war; and he used history as a stock of examples to exemplify his theories, arguing that the education of naval officers should be based on a rigorous study of history. Mahan's framework derived from Jomini, and emphasized strategic locations (such as choke points, canals, and coaling stations), as well as quantifiable levels of fighting power in a fleet. Mahan also believed that in peacetime, states should increase production and shipping capacities and acquire overseas possessions, though he stressed that the number of coal fueling stations and strategic bases should be limited to avoid draining too many resources from the mother country.

The primary mission of a navy was to secure the command of the sea, which would permit the maintenance of sea communications for one's own ships while denying their use to the enemy and, if necessary, closely supervise neutral trade. Control of the sea could be achieved not by destruction of commerce but only by destroying or neutralizing the enemy fleet. Such a strategy called for the concentration of naval forces composed of capital ships, not too large but numerous, well-manned with crews thoroughly trained, and operating under the principle that the best defense is an aggressive offense.

Mahan contended that with a command of the sea, even if local and temporary, naval operations in support of land forces could be of decisive importance. He also believed that naval supremacy could be exercised by a transnational consortium acting in defense of a multinational system of free trade. His theories, expounded before the submarine became a serious factor in warfare, delayed the introduction of convoys as a defense against the Imperial German Navy 's U-boat campaign during World War I. By the 1930s, the U.S. Navy had built long-range submarines to raid Japanese shipping; but in World War II, the Imperial Japanese Armed Forces, still tied to Mahan, designed its submarines as ancillaries to the fleet and failed to attack American supply lines in the Pacific. Mahan's analysis of the Spanish-American War suggested to him that the great distances in the Pacific required the American battle fleet to be designed with long-range striking power.

Mahan believed first, that good political and naval leadership was no less important than geography when it came to the development of sea power. Second, Mahan's unit of political analysis insofar as sea power was concerned was a transnational consortium, rather than a single nation state. Third, his economic ideal was free trade rather than autarky. Fourth, his recognition of the influence of geography on strategy was tempered by a strong appreciation of the power of contingency to affect outcomes.

In 1890, Mahan prepared a secret contingency plan for war between the British Empire and the United States. Mahan believed that if the Royal Navy blockaded the East Coast of the United States, the US Navy should be concentrated in one of its ports, preferably New York Harbor with its two widely separated exits, and employ torpedo boats to defend the other harbors. This concentration of the U.S. fleet would force the British to tie down such a large proportion of their navy to watch the New York exits that other American ports would be relatively safe. Detached American cruisers should wage "constant offensive action" against the enemy's exposed positions; and if the British were to weaken their blockade force off New York to attack another American port, the concentrated U.S. fleet could capture British coaling ports in Nova Scotia, thereby seriously weakening British ability to engage in naval operations off the American coast. This contingency plan was a clear example of Mahan's application of his principles of naval war, with a clear reliance on Jomini's principle of controlling strategic points.