The work of this patrol system is not to be restricted, however, to getting and transmitting information. Certain of the craft must be armed sufficiently to drive off hostile craft, trying to drag or countermine the defensive mine-fields; some must be able to add to the defensive mine-fields by planting mines, and some must be able to pilot friendly ships through the defensive mine-fields; others still must be able to countermine, drag, and sweep for any offensive mines that the enemy may plant. Vessels for this patrol work do not have to be very large; in fact, for much of the work in the mine-fields, it were better if they were small, by reason of the ability of small vessels to turn in restricted spaces. It would seem that for the patrol service, the vessels of the Revenue Marine and Lighthouse Service (coast guard) are ideally adapted; but, of course, there are only a few in total. These would have to be supplemented by small craft of many kinds, such as tugs, fast motor-boats, fishing-boats, and trawlers. To find men competent to man such vessels and do the kind of work required would not be so difficult as to get men competent to man the more distinctive fighting ships. Good merchant sailors, fishermen, and tugboat men would fit into the work with considerable ease, and in quite a short time. Strategy declares, however, that a coast guard may be needed a very short time after war breaks out; and that the vessels and the men, with all the necessary equipment and all the necessary organization and training, should be put into actual operation beforehand. Not only the fleet, however, but all the bureaus and offices of the Navy Department, all the navy-yards, and an the radio stations, recruiting stations, hydrographic offices, training stations, and agencies for securing information from foreign countries, will have to pass instantly from a peace basis to a war basis. To do these things quickly and correctly many preliminaries must be arranged; but if the General Staff prepares good plans beforehand, arranges measures which will insure that the plans shall be promptly carried out, and holds a few mobilization drills to test them, the various bureaus and offices in the department can do the rest. If the fires have all been lighted, the engine gotten ready, and the boilers filled in time, the engineer may open the throttle confidently, when the critical time arrives, for the engine will surely do its part.