Verdun, about a dozen permanent works absolutely fixed and ascertainable upon the map, and covering altogether but a few acres, constituted the defence of the town.  Before September was out the heavy guns had been moved to trenches far advanced into the field to the north and east, temporary rails had been laid down to permit their lateral movement—­that is, to let them shift from a place where they had perhaps been spotted to a new place, under cover of darkness, and the sectors thus thrown out in front of the old fortifications in this improvised mobile fashion were at least three times as long as the line made by the ring of old forts, while the area that had to be searched was perhaps a hundred times as large.  For in the place of the narrowly restricted permanent fort, with, say, ten heavy guns, you had those same ten heavy guns dotted here and there in trenches rapidly established in half a dozen separate, unknown, and concealed spots, along perhaps a mile of wooded hill, and free to operate when moved over perhaps double that front.

IV. In Grand Strategy a German general theory of strategics was opposed to a French general theory of strategics, and upon which of the two should prove right depended, much more than on any of the previous points, the ultimate issue of the campaign.

This is far the most important point for the reader’s consideration.  It may be said with justice that no one can understand this war who has not grasped the conflict between these two fundamental conceptions of armed bodies in action, and the manner in which (by the narrowest and most fortunate margin!) events in the first phase of the war justified the French as against the German school.

I must therefore beg the reader’s leave to go somewhat thoroughly into the matter, for it is the foundation of all that will follow when we come to the narration of events and the story of the Western battle which began in the retreat from the Sambre and ended in the Battle of the Marne.

The first postulate in all military problems is that, other things being equal, numbers are the decisive factor in war.  This does not mean that absolute superiority of numbers decides a campaign necessarily in favour of the superior power.  What it means is that in any particular field, if armament and discipline are more or less equal on the two sides, the one that has been able to mass the greater number in that field will have the victory.  He will disperse or capture his enemy, or at the least he will pin him and take away his initiative—­of which word “initiative” more later.  Now, this field in which one party has the superior numbers can only be a portion of the whole area of operations.  But if it is what is called the decisive portion, then he who has superior numbers in the decisive time and place will win not only there but everywhere.  His local victory involves consequent success along the whole of his line.