For all these reasons, it is highly desirable--it is essential to adequate preparation--that vessels should be kept in a state of material readiness that is practically perfect. Every vessel on board of which defects in material develop after she shall have been put into service, when war breaks out, will be a liability instead of an asset. She will be able to render no effective service, and she will require the expenditure of energy by officers and men, and possibly the assistance of other vessels, when their services are needed for other work. But the problem of how to keep reserve vessels in a state of material readiness is easier than the problem of how to keep the reserve men in a state of personnel readiness, which will insure their reporting on board of the reserve ships quickly enough and with adequate training. This problem is so difficult, and its solution is so important, that in Great Britain, France, Germany, Japan, and doubtless other navies, men are compelled to go into the reserves, and to remain in for several years after completing their periods of service in the regular navy. In this way, no breaking away from the navy occurs until after reserve service has been completed, and every man who enlists remains in the navy and is subject to its discipline until his reserve period has been passed. Thus the question of the reserve is a question that has been answered in those countries, and is therefore no longer a question in them. If battleship _A_ in any of those countries is to be mobilized, the government knows just who are to go on board and when; and knows that every man has recently served in the regular navy, has been kept in training ever since he left it, and that he is competent to perform the duties of his allotted station in battleship _A_. The problem of getting into service the ships that are to be gotten from the merchant service is more difficult, and is perhaps of more importance; that is, it is more important to get into the service some vessels from the merchant service than some reserve ships; more important, for instance, to get colliers to serve the fleet with coal than to commission some antiquated cruisers. Naturally, the number and kinds of ships that need to be provided will depend on the nature of the war--whether, for instance, a very large force is to be sent to the other side of the world, to meet a powerful fleet there, or whether a sudden attack on our Atlantic coast is to be repelled. The difference, however, is largely numerical; so that if the plans provide for a sufficient number to take part in the distant expedition, it will be easy to get the appropriate number to meet a coast attack. To receive an attack upon the coast, however, provision must be made for vessels and men not needed on an expedition across the seas--that is, for vessels and men that will defend the coast itself from raids and similar expeditions.