IN World War II sea power reached the culmination of its influence on history. The greatest of air wars and the one which saw the most titanic battles of all time on land was also the greatest of naval wars -- not alone in the magnitude of naval operations but also in the degree to which those operations contributed to final victory. It could hardly have been otherwise in a war which was truly global, in which the pooling of resources of the great Allies depended upon their ability to traverse the sea, and in which American men and materials, including aircraft, hammered and defeated the enemy in remote theaters which could be adequately serviced only by sea. Yet this unparalleled accomplishment of Allied sea power occurred in a war during which the very existence of navies was threatened. Although the land-based airplane was the original cause of the threat, the nature of the crisis which Allied sea power met and overcame cannot be adequately described merely in terms of ship versus aircraft. The menace of the enemy airplane was intensified by the insufficiency of cargo vessels and warships. That shortage was in large part responsible also for the successes of the German U-boat arm; and that in turn also affected the issue between planes and ships. Besides, the utility of sea power must be interpreted in terms not of the ability of the warship to defend itself, but rather of the ability of navies to carry out their traditional functions. The two are of course related, but it is important to remember that the effects of enemy aircraft on our naval strategy is by no means summed up in a tabulation of ships damaged or destroyed by them. One way to preserve ships is to minimize their exposure to danger. Such a procedure may be necessary to preserve the nucleus of a fleet, but as a general rule warships cease to be worth preserving to the extent that preoccupation with their preservation results in the abandonment of their functions. Thus, the most fruitful way of discussing tactical and strategic changes, especially as they influenced our conduct of the Pacific war, is to describe the steps by which our Navy was gradually enabled to dominate the maritime struggle. The function of sea power has traditionally been to achieve and maintain "command of the sea." This time-honored and somewhat cryptic phrase connotes simply the ability to use the sea and to deny its use to the enemy. The test of "command" is the exclusion of enemy shipping from an area in which one's own shipping continues to operate. The uses of command are many, ranging from those which are offensive in nature (e.g. invasion of an enemy coast, or economic blockade) to those which are purely defensive (e.g. the defense of one's coasts against overseas invasion, or protection of shipping). But where it exists at all, command is always basically the same in character.