[26] As a matter of fact, the extreme range of the present armament of American harbor defenses is 23,000 yards. This is not a reliably effective fighting range, and is merely stated as being the extreme range, “under crucial test,” of the 12-inch steel rifled mortars. The rifled guns as now mounted have a range of not more than 13,000 yards. Battle-ships now being constructed are armed with 15 and 16-inch guns that can outrange the extreme theoretical range of the mortars. [27] Harbor defenses are not constructed, necessarily, to protect places near them. Their purpose is to prevent a naval force from occupying an important harbor whose possession would open the way to rich territory or lay commerce prostrate. Therefore it is no defect in the construction of the Long Island entrance defenses that it is possible to bombard coast places near them. It is physically impossible ever to defend all the places on our coast with fortifications. [28] The Army War College has repeatedly called attention to the urgent need of the mobile army for siege artillery and for the organization of an efficient body of troops trained in its use to be _available whenever needed_. “Ammunition on hand for artillery, 38 per cent. of amount required.” (See report of Army Board, and Secretary of War Garrison’s statement to House Appropriations Committee, 1915.) Another estimate in the possession of the author would indicate that the ammunition on hand for _heavy_ artillery is only about 15 per cent. of the amount required. [29] Troops cannot be landed with as little delay as this. But naval tactics assume as a matter of course that an advance body of bluejackets, trained for beach and surf work, can effect an immediate landing if protected from attack. [30] Lord Cochran landed 18,000 men on the open coast of Chile in five hours, with some guns. The surf conditions there are extremely hazardous. [31] American submarines now in commission do not carry more than one 3-inch rapid fire gun. It is set in a watertight compartment from which it is elevated when the vessel is on the surface. Armaments of destroyers are: Ammen class, five 3-inch rapid fire 30 cal. rifles; Aylwin class, four 4-inch rapid fire 50 cal. rifles; Bainbridge class, two 3-inch rifles and five 6-pounders rapid fire. [32] Submarine wire entanglements are being used effectively for the protection of harbors during the present war. The wire cannot resist cutting much more than twine can. It stops the submarine by menacing it with being entangled and trapped. A submarine caught under water cannot be cleared by its crew. The utmost the men can do is to try to reach the surface by putting on “special escape helmets” and emerging through the air-locks.