Mahan used history as a stock of lessons to be learned--or more exactly, as a pool of examples that exemplified his theories. Mahan believed that national greatness was inextricably associated with the sea, with its commercial usage in peace and its control in war. His goal was to discover the laws of history that determined who controlled the seas. His theoretical framework came from Jomini, with an emphasis on strategic locations (such as chokepoints, canals, and coaling stations), as well as quantifiable levels of fighting power in a fleet. The primary mission of a navy was to secure the command of the sea. This not only permitted the maintenance of sea communications for one's own ships while denying their use to the enemy but also, if necessary, provided the means for close supervision of neutral trade. This control of the sea could not be achieved by destruction of commerce but only by destroying or neutralizing the enemy fleet. This called for concentration of naval forces composed of capital ships, not unduly large but numerous, well manned with crews thoroughly trained, and operating under the principle that the best defense is an aggressive offense.
