The main object of this book is to present a phalanx of facts upon the subject of the defenseless condition of this country, and to show what must be done, and done quickly, in order to avert the most dire calamity that can fall upon a people-that of merciless invasion by a foreign foe, with the horrors of which no pestilence can be compared. We should bring a lesser calamity upon ourselves by abolishing our quarantine system against the importation of deadly disease and inviting a visitation like the great London Plague, or by letting in the Black Death to sweep our country as it swept Europe in the Middle Ages, than by neglecting our quarantine against war, as we are neglecting it, thereby inviting the pestilence of invasion.