The naval operations in the late war with Spain demonstrated the value of submarine mines as an element of coastal defence against an attacking fleet. Their value was abundantly proved during the blockade of Santiago, the actual objective of which was the capture or destruction of Cervera's Squadron.

Apart from its enormous destructive power, the submarine mine exercises a powerful moral effect on the enemy, because of its invisibility and the practical impossibility of determining its exact location. It is the most quickly available of all systems of coastal defence, and unlike other means of offence, its cost is all out of proportion to the damage it can inflict. "It is pre-eminately the weapon of the weak."