Secondly, the decisive importance to the ultimate issue, of this great fortified zone of country lying before my eyes in the winter twilight; which stretches, as my map tells me, right across Northern France, from the Ypres salient, in front of Lille and Douai, through this point south-west of Cambrai where I am standing, and again over those distant slopes to the south-west over which the shades are gathering, to St. Quentin and St. Gobain.  These miles of half-effaced and abandoned trenches, with all those scores of other miles to the north-west and the south-east which the horizon covers, represent, as I have said, the culminating effort of the war; the last effective stand of the German brought to bay; the last moment when Ares, according to Greek imagination, “the money changer of war,” who weighs in his vast balance the lives of men, still held the balance of this mighty struggle in some degree uncertain.  But the fortress fell; the balance came down on the side of the Allies, and from that moment, though there was much fighting still to do, the war was won.

As to the actual meaning in detail of the “Hindenburg” or “Siegfried” line, let me, for the benefit of those who have never seen even a yard of it, come back to the subject presently, helped by a captured German document, and by a particularly graphic description of it, written by an officer of the First Army.

But first, with the scene still before me—­the broken bridge, the ruined lock, the splendid trench at my feet, and those innumerable white lines on the far hill-side—­let me recall the great story of the six months which preeceded the attack of Sir Julian Byng’s Third Army on this bank of the Canal du Nord.

It was on Monday, March 25th, that at Doullens, a small manufacturing town, lying in a wooded and stream-fed hollow not far from Amiens, there took place the historic meeting of the leading politicians and generals of the war, which ended in the appointment of Marshal Foch to the supreme military command of the Allied forces in France.  I remember passing Doullens in 1917, dipping down into the hollow, climbing out of it again on to the wide upland leading to Amiens, and idly noticing the picturesqueness of the place.  But there must be a house and a room in Doullens, which ought already to be marked as national property, and will certainly be an object of travel in years to come for both English and French; no less than that factory to the west of Verdun where Castelnau and Petain conferred at the sharpest crisis of the immortal siege.  For there—­so it is generally believed—­the practical sense and generous temper of the British Commander brought about that change in the whole condition of the war which we know as the “unity of command.”  Sunday, March 24th, had been a particularly bad day in that vast defensive battle which, in General Haig’s phrase, “strained the resources of the Allies to the uttermost.”  There had been difficulties and misunderstandings also—­perfectly natural in the circumstances—­with the French Army on the right of the British line.  Yet never was a perfect co-ordination of the whole Allied effort in face of the German attack so absolutely essential.