"I only know two things: Firstly, that a very great number of them, if not all, realised only too well that the enemy had discovered our plans; and, secondly, that the only ones who did not start were those who could not, because they had been either killed or wounded." And now turn with me to the top of all--the General Staff of the Army in France--the brain of the whole mighty movement. It was with no light emotion that I found myself last January, on a bitter winter day, among a labyrinth of small rooms running round the quadrangle of the old Ecole Militaire at Montreuil, while they were still full of Staff officers gathering up the records of the war. Here, or in the Staff train moving with the Commander-in-Chief along the front, the vast organisation of battle culminated in a few guiding brains from which energising and unifying direction flowed out to all parts of the field of war. Here were the heads of Q., of A., of G.--in other words, of Supply, Reinforcement, and Operations. In a bare room, with a few chairs and tables and an iron stove, the Director of Operations was at work; close by was the office of the Quartermaster-General, while up another staircase and along another narrow passage were the quarters of the Adjutant-General; and somewhere, I suppose, in the now historic building, was or had been the office of the Commander-in-Chief himself. The Intelligence Department was not far off, I knew, in the old town; I had been its grateful guest in 1917. The directing Intelligence of the Army flowed out from here to the front, while from the front, at the same time, there came back a constant stream of practical knowledge and experience, keeping the life of G.H.Q. perpetually fresh, correcting theory by experience and kindling experience by theory. The complexities and responsibilities of the work done were vast indeed.