It is clear that four great European Powers and some smaller ones cannot engage in war without shaking the fabric of European civilisation to its foundations. The tramp of fifteen million armed men is the greatest social and economic fact of the present day, and indeed of the present generation. These millions of combatants have to be clothed, fed, armed, transported, and tended in health and in sickness; they are non-producers for the time, consuming in large quantities the staple commodities of life, and calling in addition for all the paraphernalia of war; sooner or later, they will desire to return to the plough and the mine, the factory and the railroad. These two facts alone are of tremendous importance. But besides this, the activity of those who stay at home is called into play in a thousand different ways, and economic and social life leave their well-trodden paths in answer to the imperious call of national necessity. Social institutions of all kinds are inevitably led into new fields of thought and action, and States are driven to untried experiments in communal activity. The usual channels of thought dry up, the flood of new ideas and of old ideas throbbing with a new life rushes on unconfined, here in the shallows, there in the deeps, presently to overflow into the old channels, cleansing their beds and giving them a new direction, and linking up in fruitful union but remotely connected streams. When fighting ceases and there comes the calm of peace, society will tend to revert to its normal functions, based on peace; but the society of yesterday can never return. Social life cannot be the same as it was before, not merely because those activities called forth by the war may persist in some form, but because of the growth of new ideas under the stimulus of the war. The struggle will almost certainly set in progress trains of thought not only connected with questions of war and peace, but with the wider questions of human destiny. Coming to a closer view of the question, we must distinguish between the immediate effects of the war which are already in evidence and the ultimate effects which will but begin to unfold themselves after the return of peace. Some of the latter results will grow out of the immediate effects; others will be more directly due to the events following on the conclusion of the war. It will also be advisable to distinguish between the economic reactions of the war, and the broader social consequences. At such an early stage it would be presumptuous and tempting Providence to attempt to forecast the future in any detail or to try to trace the play and interplay of the various forces going towards the making of the future. This chapter will be concerned with broad tentative generalisations on quite simple lines.