But while this is the absolute tendency of war against commerce, common to all cases, the relative value varies greatly with the countries having recourse to it. It is a species of hostilities easily extemporized by a great maritime nation; it therefore favors one whose policy is not to maintain a large naval establishment. It opens a field for a sea militia force, requiring little antecedent military training. Again, it is a logical military reply to commercial blockade, which is the most systematic, regularized, and extensive form of commerce-destruction known to war. Commercial blockade is not to be confounded with the military measure of confining a body of hostile ships of war to their harbor, by stationing before it a competent force. It is directed against merchant vessels, and is not a military operation in the narrowest sense, in that it does not necessarily involve fighting, nor propose the capture of the blockaded harbor. It is not usually directed against military ports, unless these happen to be also centers of commerce. Its object, which was the paramount function of the United States Navy during the Civil War, dealing probably the most decisive blow inflicted upon the Confederacy, is the destruction of commerce by closing the ports of egress and ingress. Incidental to that, all ships, neutrals included, attempting to enter or depart, after public notification through customary channels, are captured and confiscated as remorselessly as could be done by the most greedy privateer. Thus constituted, the operation receives far wider scope than commerce-destruction on the high seas; for this is confined to merchantmen of belligerents, while commercial blockade, by universal consent, subjects to capture neutrals who attempt to infringe it, because, by attempting to defeat the efforts of one belligerent, they make themselves parties to the war. In fact, commercial blockade, though most effective as a military measure in broad results, is so distinctly commerce-destructive in essence, that those who censure the one form must logically proceed to denounce the other. This, as has been seen, Napoleon did; alleging in his Berlin Decree, in 1806, that war cannot be extended to any private property whatever, and that the right of blockade is restricted to _fortified_ places, actually invested by competent forces. This he had the face to assert, at the very moment when he was compelling every vanquished state to extract, from the private means of its subjects, coin running up to hundreds of millions to replenish his military chest for further extension of hostilities. Had this dictum been accepted international law in 1861, the United States could not have closed the ports of the Confederacy, the commerce of which would have proceeded unmolested; and hostile measures being consequently directed against men’s persons instead of their trade, victory, if accomplished at all, would have cost three lives for every two actually lost.