[85] “When the defenses outside the Continental United States are provided for, there will remain for home gun defenses 176 officers and 7,543 enlisted men, _which is about one-third of one relief_.”--Page 15, Report, Chief of Coast Artillery, U. S. A., for year ended June 30, 1914. [86] “The searchlight project is approximately 50 per cent. completed.... The fire-control system may be said to be approximately 60 per cent. completed.... Installation of power generating and distributing equipment is 25 per cent. completed.... Submarine mine structures are 83 per cent. completed.”--Report, Chief of Coast Artillery, U. S. A., for year ended June 30, 1914. [87] Regular manning detail for Boston defenses, twelve companies of Coast Artillery. These have seven systems of defense to maintain. The companies are not enlisted to their full strength. Even if they were, there would be less than two hundred men to each defense. This is not sufficient for any sustained action at the big guns alone. A sufficiently energetic enemy, even if he might not damage the works, could wear out the men by incessant attack for a few days and nights. There certainly would not be men enough to provide for outlying defense against landing parties. [88] These are all vitally necessary parts of the defense of the Boston harbor forts. They are only a small part of what would have to be done in case of naval attack. The data used here are not theoretical. They have been developed by actual test. [89] So developed in sea and land maneuvers undertaken for the purpose of establishing the very points here mentioned. [90] It is estimated, from careful calculations, that to put out of action a searchlight at night with shipfire at a range of 6,000 yards, more than a thousand shots from 3-inch guns should be required. The fact is mentioned here to illustrate the great strength of harbor defenses against fire from the sea, if there be enough mobile troops on the land to prohibit destruction by landing parties. [91] That the American harbor defense system and construction are of the very highest type, has been acknowledged many times by the technical experts of the world. More than once the author has heard foreign officers express the belief that they were practically impregnable to naval fire, providing they were fully supplied and equipped with the material necessary for continuous defense. [92] A generous system of reliefs is imperative in harbor defenses during war. Peace time maneuvers have developed the fact that the mere strain of incessant watchfulness while waiting for an enemy who may appear at unexpected points suddenly, is so great that unless the men have frequent relief, they cannot exert that concentrated energy which is needed instantly in the crisis.