Mahan on naval warfare

by A. T. Mahan

There is another sense in which a navy is regarded as defensive; namely, that the existence of an adequate navy protects from invasion by commanding the sea. That is measurably and in very large degree true, and is a strategic function of great importance; but this is a wholly different question from that of the defensive strength of seaports, of strategic points, with which we are now dealing. It therefore will be postponed, with a simple warning against the opinion that because the navy thus defends there is no need for local protection of the strategic ports; no need, that is, for fortifications. This view affirms that a military force can always, under all circumstances, dispense with secure bases of operations; in other words, that it can never be evaded, nor know momentary mishap.

I have now put before you reasons for rejecting the opinion that the navy is the proper instrument, generally speaking, for coast defense in the narrow sense of the expression, which limits it to the defense of ports. The reasons given may be summed up, and reduced to four principles, as follows:

1. That for the same amount of offensive power, floating batteries, or vessels of very little mobility, are less strong defensively against naval attack than land works are.

2. That by employing able-bodied seafaring men to defend harbors you lock up offensive strength in an inferior, that is, in a defensive, effort.

3. That it is injurious to the morale and skill of seamen to keep them thus on the defensive and off the sea. This has received abundant historical proof in the past.

4. That in giving up the offensive the navy gives up its proper sphere, which is also the most effective.

B. Offensive Strength.—The offensive strength of a seaport, considered independently of its strategic situation and of its natural and acquired resources, consists in its capacity:

1. To assemble and hold a large military force, of both ships of war and transports.

2. To launch such force safely and easily into the deep.

3. To follow it with a continued support until the campaign is ended. In such support are always to be reckoned facilities for docking, as the most important of all supports.