Of course, no community can become fully self-sustaining under modern conditions, by use of the modern state of the industrial arts, except by recourse to such drastic measures of repression as would reduce its total efficiency in an altogether intolerable degree. This will hold true even of those nations who, like Russia or the United States, are possessed of extremely extensive territories and extremely large and varied resources; but it applies with greatly accentuated force to smaller and more scantily furnished territorial units. Peoples living under modern conditions and by use of the modern state of the industrial arts necessarily draw on all quarters of the habitable globe for materials and products which they can procure to the best advantage from outside their own special field so long as they are allowed access to these outlying sources of supply; and any arbitrary limitation on this freedom of traffic makes the conditions of life that much harder, and lowers the aggregate efficiency of the community by that much. National self-sufficiency is to be achieved only by a degree of economic isolation; and such a policy of economic isolation involves a degree of impoverishment and lowered efficiency, but it will also leave the nation readier for warlike enterprise on such a scale as its reduced efficiency will compass. So that the best that can be accomplished along this line by the dynastic statesmen is a shrewd compromise, embodying such a degree of isolation and inhibition as will leave the country passably self-sufficient in case of need, without lowering the national efficiency to such a point as to cripple its productive forces beyond what will be offset by the greater warlike readiness that is so attained. The point to which such a policy of isolation and sufficiency will necessarily be directed is that measure of inhibition that will yield the most facile and effective ways and means of warlike enterprise, the largest product of warlike effectiveness to be had on multiplying the nation's net efficiency into its readiness to take the field. Into any consideration of this tactical problem a certain subsidiary factor enters, in that the patriotic temper of the nation is always more or less affected by such an economic policy. The greater the degree of effectual isolation and discrimination embodied in the national policy, the greater will commonly be its effect on popular sentiment in the way of national animosity and spiritual self-sufficiency; which may be an asset of great value for the purposes of warlike enterprise.