The Title story of this volume was written about eighteen months before the outbreak of the war, and was intended to direct public attention to the great danger which threatened this country. It is a matter of history how fully this warning has been justified and how, even down to the smallest details, the prediction has been fulfilled. The writer must, however, most thankfully admit that what he did not foresee was the energy and ingenuity with which the navy has found means to meet the new conditions. The great silent battle which has been fought beneath the waves has ended in the repulse of an armada far more dangerous than that of Spain.