The regular mine-laying fleets of the powers at war are composed of the following vessels, all of which are fitted with special apparatus for the work. Submarine mines can, however, be laid by any vessel, and it is therefore almost impossible to say exactly what ships are engaged in this work. Both Germany and Austria have converted a large number of their merchantmen into mine-layers. England, in reply, has converted a large number of small steamers into mine-sweepers. Russia is a strong believer in explosive mines, and has strewn the gulfs of Finland and Riga with them. Japan, being on the offensive, is employing more mine-sweepers than layers. France has an elaborate system of submarine mine defence for all her important harbours, and maintains a small fleet at each base, known as the “defence mobile.” These vessels are all capable of both mine-laying and sweeping.

The submarine mine is primarily the defence of the weaker naval power, and therefore a fleet acting on the defensive, either temporarily or permanently, requires more mine-layers than mine-sweepers, but the reverse is naturally the case with a fleet acting on the offensive. Although this may be taken as a general rule, it does not imply that a strong naval power like Great Britain, whose policy is attack and not defence, needs no mines or mine-layers. On the contrary, the laying of counter mines is one of the ways of destroying an enemy’s mine-field; and even the strongest fleet cannot guard every portion of a long coast line with many harbours exposed to attack. The judicious laying of mine-fields will often prevent raids by hostile submarines and torpedo-boats; and will limit the theatre of operations, as was done by the British Navy in the southern portion of the North Sea in October, 1914. The axiom that a really strong navy needs to be strong in every branch, therefore holds good in this, as in all other respects.

Mine-Laying Fleets.

Great Britain.